Switch to Google style docstrings

Napoleon is the Sphinx extension used to parse the docstrings.
Use 'napoleon' from 'sphinxcontrib'

For use with Sphinx under v1.3
Use Python 3.4 intersphinx mapping
Use 'open' instead of 'file' for argument types
Merge pull request #12 from maelstrom59/napoleon

Use Napoleon to parse 'Google style' docstrings