switch out distutils.core for setuptools

[alisaifee]

1. less code in setup.py
2. allows using python setup.py develop to make ansible available on sys.path from a checkout

[mpdehaan]

So there's a lot more than just sys.path you want to set up, which is why we have the

source ./hacking/env-setup script

This also becomes an additional build dependency

see replies here also

http://stackoverflow.com/questions/6344076/differences-between-distribute-distutils-setuptools-and-distutils2

the hacking/env-setup script provides all of that setup and a bit more.

The extra code is not a concern ATM.