docs: Rename argarse_ext to ext_argparse.
docs: Replace sphinxcontrib.issuetracker with my own extension.
docs.ext_github: Fix Python 2 compatibility.
Add ~/Applications to search path for VLC

This adds the ~/Applications` to the search path for the VLC.app on Darwin (Mac OS X).
It's for those that have installed VLC to their account only.
Merge pull request #454 from maxnordlund/patch-1

Add ~/Applications to search path for VLC