Fixed #63 - `use_directory_urls` option has no effect.

- The `use_directory_urls` option is now passed forward to the
SiteNavigation object in order to correctly generate links to the
target file when needed.
- The post-processing of the HTML generated by converting from Markdown
now takes the `use_directory_urls` option passed to the SiteNavigation
object into account when changing anchor targets.
- The dev server mode (mkdocs serve) still ignores the
`use_directory_urls` option in order to have user-friendly URLs.
- There is a new test case for post-processing converted Markdown when
  `use_directory_urls` is `False`.
Fixes #65 - Links to other files within documentation are broken on Python 2.6

There was a bug in `posixpath.relpath()` in this version of Python. The
bug was worked around by a verification of the corner case were the
`start` argument is the root directory.
Fixes indentation issues which caused lint errors.

Those errors were causing the `runtests` script to fail.
Fixes location of static assets.

The previous commit made `base_url` incorrectly empty.
Windows: Don't use os.path.join() for URL paths.
Windows: Use posixpath in nav.FC.make_absolute()

nav.FileContext.make_absolute() is only used to compare
links to entries in mkdocs.yml, so it makes sense for it
to only use POSIX-style paths.

Without this, the site fails to build because it checks for
a Windows-style path in a list of POSIX paths in
build.PathToURL.__call__().

This is the last change required to build the mkdocs site
on Windows.
Updated setup.py to use entry_points['console_scripts'] instead of scripts.

This makes a "mkdocs" command on Windows/OSX/Linux without any platform-specific code in setup.py.

I think this is the preferred way to install a Python command with setuptools.

It is, at least, the method used by:

* [flake8](https://bitbucket.org/tarek/flake8/src/8ee94d1eeea36e835583b68c59682bfc3684fab9/setup.py?at=default)
* [coverage.py](https://bitbucket.org/ned/coveragepy/src/ca875e739048c3b333e862471b89d55e3c7b7170/setup.py?at=default)
* [Fabric](https://github.com/fabric/fabric/blob/master/setup.py)
* Many others

In the past, I had to change imports willy-nilly or add
"from __future__ import absolute_imports" to a bunch of files.
This is because I was renaming "mkdocs" to "mkdocs.py" instead of "main.py",
and the module-vs-script name clash was confusing imports from other files.
flake8 fixes in main.py (How did this ever pass?)
Merge pull request #92 from ericholscher/master

Detect absolute URL’s in the extra_* path.
Update the menu/toc to support the new nav code changes.

fixes gh-110
Merge pull request #122 from edbrannin/windows-command

Fix "mkdocs" command creation in Windows
Merge pull request #124 from ryanneufeld/fix-gh-110

Update the menu/toc to support the new nav code changes.
Merge pull request #121 from edbrannin/windows-paths

Fix path-handling on Windows
Improve whitespace around css and script tags
Remove reference to the `config` variable in the template files
Add support for extra_css and extra_javascript in all the themes
Avoid repeated overwrites of config['extra_*']

Fixes #133
Merge pull request #136 from jimporter/config-var

Remove reference to the `config` variable in the template files for custom themes
Merge pull request #90 from jimporter/extra-css

Add support for extra_css and extra_javascript in all the themes
Merge pull request #134 from dnrce/bug/133-wrong-extra-media-paths

Avoid repeated overwrites of config['extra_*']