Building sphinx docs for src/python/twitter/commons

I added a docs folder for the python twitter.commons stuff. The source for much documentation is an email thread from Brian Wickman so it should be mostly correct.

I also did some autodocing to pull in docs in docstrings in the source. This occasionally necessitated sphinxifying the docstrings to supress warnings/errors or rendering bugs.

Build the docs by installing sphinx and running:

    sphinx-build -b html -d ./docs/_build/doctrees  ./docs ./docs/_build/html 

from the src/python/twitter/commons directory.