fix pip installation error

```pip install ColanderAlchemy```
currently fails with an IOError, as README.rst is not in the current directory, and setup.py reads README.rst to ``long_description``.

See log below:

```
------------------------------------------------------------
/home/kevin/tmp/ca/bin/pip run on Sun Apr 21 17:16:58 2013
Downloading/unpacking ColanderAlchemy

  Getting page http://pypi.python.org/simple/ColanderAlchemy
  URLs to search for versions for ColanderAlchemy:
  * http://pypi.python.org/simple/ColanderAlchemy/
  Getting page https://github.com/stefanofontanelli/ColanderAlchemy
  Analyzing links from page http://pypi.python.org/simple/ColanderAlchemy/
    Found link http://pypi.python.org/packages/source/C/ColanderAlchemy/ColanderAlchemy-0.1b5.tar.gz#md5=bc0dc7d1a64a7d9e759521f6455cd75f (from http://pypi.python.org/simple/ColanderAlchemy/), version: 0.1b5
    Found link http://pypi.python.org/packages/source/C/ColanderAlchemy/ColanderAlchemy-0.1b4.tar.gz#md5=f50536e8342ec979c3d59977ea12ae92 (from http://pypi.python.org/simple/ColanderAlchemy/), version: 0.1b4
    Found link http://pypi.python.org/packages/source/C/ColanderAlchemy/ColanderAlchemy-0.1b3.tar.gz#md5=4137050ac8d1d9ea4c3db171ab64bc00 (from http://pypi.python.org/simple/ColanderAlchemy/), version: 0.1b3
    Found link http://pypi.python.org/packages/source/C/ColanderAlchemy/ColanderAlchemy-0.1b.tar.gz#md5=a0854c0abc8f4fa1ba5cf7882d32473d (from http://pypi.python.org/simple/ColanderAlchemy/), version: 0.1b
    Found link http://pypi.python.org/packages/source/C/ColanderAlchemy/ColanderAlchemy-0.1b2.tar.gz#md5=0d4ad07076835fd43fc6c3ac3280ada8 (from http://pypi.python.org/simple/ColanderAlchemy/), version: 0.1b2
    Found link http://pypi.python.org/packages/source/C/ColanderAlchemy/ColanderAlchemy-0.1b6.tar.gz#md5=0f75e79d0803fe5d542e1faadc05d9df (from http://pypi.python.org/simple/ColanderAlchemy/), version: 0.1b6
    Found link http://pypi.python.org/packages/source/C/ColanderAlchemy/ColanderAlchemy-0.1.0a.tar.gz#md5=4b81c163972d204f3a27c54e7db19576 (from http://pypi.python.org/simple/ColanderAlchemy/), version: 0.1.0a
    Found link http://pypi.python.org/packages/source/C/ColanderAlchemy/ColanderAlchemy-0.2a1.tar.gz#md5=c4dd67b060dc314a4d1824759b014ac1 (from http://pypi.python.org/simple/ColanderAlchemy/), version: 0.2a1
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy (from http://pypi.python.org/simple/ColanderAlchemy/); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/issues/new (from http://pypi.python.org/simple/ColanderAlchemy/); not a file
    Skipping link http://readthedocs.org/docs/colanderalchemy/en/latest/index.html (from http://pypi.python.org/simple/ColanderAlchemy/); unknown archive format: .html
    Skipping link https://twitter.com/stefontanelli (from http://pypi.python.org/simple/ColanderAlchemy/); not a file
    Skipping link http://docs.pylonsproject.org/projects/colander/en/latest/ (from http://pypi.python.org/simple/ColanderAlchemy/); not a file
    Skipping link http://www.opensource.org/licenses/mit-license.php (from http://pypi.python.org/simple/ColanderAlchemy/); unknown archive format: .php
    Skipping link http://www.sqlalchemy.org/ (from http://pypi.python.org/simple/ColanderAlchemy/); not a file
    Skipping link http://docs.pylonsproject.org/projects/deform/ (from http://pypi.python.org/simple/ColanderAlchemy/); not a file
  Analyzing links from page https://github.com/stefanofontanelli/ColanderAlchemy
    Skipping link https://github.com/opensearch.xml (from https://github.com/stefanofontanelli/ColanderAlchemy); unknown archive format: .xml
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    Skipping link https://github.com/apple-touch-icon-114.png (from https://github.com/stefanofontanelli/ColanderAlchemy); unknown archive format: .png
    Skipping link https://github.com/apple-touch-icon-144.png (from https://github.com/stefanofontanelli/ColanderAlchemy); unknown archive format: .png
    Skipping link http://github-media-downloads.s3.amazonaws.com/github-logo.svg (from https://github.com/stefanofontanelli/ColanderAlchemy); unknown archive format: .svg
    Skipping link https://github.com/_sockets (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/favicon.ico (from https://github.com/stefanofontanelli/ColanderAlchemy); unknown archive format: .ico
    Skipping link https://a248.e.akamai.net/assets.github.com/assets/github-3dae77b1344d5de8d1c932d28c3904033713ed8b.css (from https://github.com/stefanofontanelli/ColanderAlchemy); unknown archive format: .css
    Skipping link https://a248.e.akamai.net/assets.github.com/assets/github2-8700f58b37c27f7b329397f20a75deb70a514871.css (from https://github.com/stefanofontanelli/ColanderAlchemy); unknown archive format: .css
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/tree/1f33f2e29edae38004b27b48f3cf640cceda659d (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/commits/master.atom (from https://github.com/stefanofontanelli/ColanderAlchemy); unknown archive format: .atom
    Skipping link https://github.com/ (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/signup (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/login?return_to=%2Fstefanofontanelli%2FColanderAlchemy (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/explore (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/search (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/features (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/blog (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/stargazers (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/network (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/pulse (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/pulls (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/issues (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/graphs (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/languages/Python (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/languages/Shell (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy#readme (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Could not parse version from link: https://github.com/stefanofontanelli/ColanderAlchemy/archive/master.zip (from https://github.com/stefanofontanelli/ColanderAlchemy)
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/archive/master.zip (from https://github.com/stefanofontanelli/ColanderAlchemy); wrong project name (not colanderalchemy)
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy.git (from https://github.com/stefanofontanelli/ColanderAlchemy); unknown archive format: .git
    Skipping link https://github.com/stefanofontanelli/git@github.com:stefanofontanelli/ColanderAlchemy.git (from https://github.com/stefanofontanelli/ColanderAlchemy); unknown archive format: .git
    Skipping link git://github.com/stefanofontanelli/ColanderAlchemy.git (from https://github.com/stefanofontanelli/ColanderAlchemy); unknown archive format: .git
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/tags (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/tree/0.1 (from https://github.com/stefanofontanelli/ColanderAlchemy); unknown archive format: .1
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/tree/master (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/commits/master (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/branches (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/find/master (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/commit/1f33f2e29edae38004b27b48f3cf640cceda659d (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/tree/master/colanderalchemy (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/commit/dcb6dc76da978505d0cbb29ea6d192d74de78fdc (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/davidjb (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/tree/master/docs (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/tree/master/tests (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/commit/414feae1ccaff0ec91d169d6187ef503778bf2c7 (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/blob/master/.gitignore (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/commit/6e88fcf11bc6affc2c0d3d4ac7f2388ff1010778 (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/blob/master/AUTHORS.txt (from https://github.com/stefanofontanelli/ColanderAlchemy); unknown archive format: .txt
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/commit/4f3e1d72bf08f8012c45eeb195c851b7f152ea37 (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/blob/master/CHANGELOG.txt (from https://github.com/stefanofontanelli/ColanderAlchemy); unknown archive format: .txt
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/commit/295a8de861967d878405e3fdbdb53e99002a84c8 (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/blob/master/LICENSE.txt (from https://github.com/stefanofontanelli/ColanderAlchemy); unknown archive format: .txt
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/commit/fb458df875735634b48d10380274e839f0ff5028 (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/blob/master/README.rst (from https://github.com/stefanofontanelli/ColanderAlchemy); unknown archive format: .rst
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/commit/2c624a3d7c3729d991cc1f7e96aaa4c47214fce4 (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/blob/master/setup.cfg (from https://github.com/stefanofontanelli/ColanderAlchemy); unknown archive format: .cfg
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/commit/f5a2ad63ff6303dbaaaad10855cbfd7f011517e3 (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/blob/master/setup.py (from https://github.com/stefanofontanelli/ColanderAlchemy); unknown archive format: .py
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/commit/5b491ebcdb9875a930e04b666ca0deed897c2042 (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/blob/master/tox.ini (from https://github.com/stefanofontanelli/ColanderAlchemy); unknown archive format: .ini
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy/commit/b85853154b31f2e50b2f98811dc0bbd95aa649dd (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy#colanderalchemy (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy#documentation (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy#installation (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy#license (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy#development-version (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/stefanofontanelli/ColanderAlchemy#support (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
    Skipping link https://github.com/about (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
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    Skipping link http://enterprise.github.com/ (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
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    Skipping link http://developer.github.com/ (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
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    Skipping link https://github.com/security (from https://github.com/stefanofontanelli/ColanderAlchemy); not a file
  Using version 0.2a1 (newest of versions: 0.2a1, 0.1b6, 0.1b5, 0.1b4, 0.1b3, 0.1b2, 0.1b, 0.1.0a)
  Downloading ColanderAlchemy-0.2a1.tar.gz

  Downloading from URL http://pypi.python.org/packages/source/C/ColanderAlchemy/ColanderAlchemy-0.2a1.tar.gz#md5=c4dd67b060dc314a4d1824759b014ac1 (from http://pypi.python.org/simple/ColanderAlchemy/)
  Running setup.py egg_info for package ColanderAlchemy

    Traceback (most recent call last):

      File "<string>", line 14, in <module>

      File "/home/kevin/tmp/ca/build/ColanderAlchemy/setup.py", line 8, in <module>

        long_description=open('README.rst').read(),

    IOError: [Errno 2] No such file or directory: 'README.rst'

    Complete output from command python setup.py egg_info:

    Traceback (most recent call last):

  File "<string>", line 14, in <module>

  File "/home/kevin/tmp/ca/build/ColanderAlchemy/setup.py", line 8, in <module>

    long_description=open('README.rst').read(),

IOError: [Errno 2] No such file or directory: 'README.rst'

----------------------------------------

Command python setup.py egg_info failed with error code 1 in /home/kevin/tmp/ca/build/ColanderAlchemy

Exception information:
Traceback (most recent call last):
  File "/home/kevin/tmp/ca/local/lib/python2.7/site-packages/pip-1.1-py2.7.egg/pip/basecommand.py", line 104, in main
    status = self.run(options, args)
  File "/home/kevin/tmp/ca/local/lib/python2.7/site-packages/pip-1.1-py2.7.egg/pip/commands/install.py", line 245, in run
    requirement_set.prepare_files(finder, force_root_egg_info=self.bundle, bundle=self.bundle)
  File "/home/kevin/tmp/ca/local/lib/python2.7/site-packages/pip-1.1-py2.7.egg/pip/req.py", line 1009, in prepare_files
    req_to_install.run_egg_info()
  File "/home/kevin/tmp/ca/local/lib/python2.7/site-packages/pip-1.1-py2.7.egg/pip/req.py", line 225, in run_egg_info
    command_desc='python setup.py egg_info')
  File "/home/kevin/tmp/ca/local/lib/python2.7/site-packages/pip-1.1-py2.7.egg/pip/__init__.py", line 256, in call_subprocess
    % (command_desc, proc.returncode, cwd))
InstallationError: Command python setup.py egg_info failed with error code 1 in /home/kevin/tmp/ca/build/ColanderAlchemy
```