First pass at building sphinx docs
change hardcoded path of sphinx-build
Fix sphinx-build call failure due to nuking environment
Put sphinx into virtualenv and stop using system sphinx
Rip sphinx out of build.py

We're having problems with the interaction between sphinx and pygments
in our test suite. For now let's back sphinx out of our main virtualenv.
Merge pull request #310 from gittip/sphinxify

First pass at building sphinx docs