Adding setup.py+MANIFEST.in for pip-full installation

Adding branch specific README.md
Zero modifications required + no more ```from dev_appserver import fix_sys_path...```.
Local ```virtualenv``` development:

  pip install --install-option="install" -e git://github.com/ssspiochld/googleappengine-python.git@pip#egg=googleappengine-python

It provides two scripts:
- appcfg.py
- dev_appserver_main.py (yeap _main)

The original root directory scripts were ```google.appengine.tools``` wrappers.
Now all packages get discovered and installed. Looks ok to fallback to the original scripts.
Otherwise small patching would be needed:
https://gist.github.com/2184014

***NOTE:*** For python2.5 runtime ignore the installation "with_statements" warnings

Adding ``package_data`` setup option for including builtins on python2.7. fixes #1

The list could be dynamically build but left static for now.