Added globaltoc sidebar option

Previously if you include the sphinx built-in “globaltoc” it comes out
completely unformatted.
Added Github link to Navigation

If the github theme and user are set this adds the Github link to the
navigation bar.
Updated README example.

Fixes #4 by removing the reference to
“guzzle_sphinx_theme.GuzzleStyle”, which no longer exists.
Merge pull request #7 from tedivm/readme

Updated README example.
Merge pull request #6 from tedivm/Github_Navigation

Added Github link to Navigation
Merge pull request #5 from tedivm/global_toc

Added globaltoc sidebar option