Automate docs version from our setup.cfg
Automate docs version from our setup.cfg

Our docs version is out of date (2.7), so this moves towards automating
this version. The version is displayed in intersphinx links and in the
title of the page. I didn't use the `readthedocs.__init__` method to
avoid an import into our docs.

rtfd/readthedocs.org,rtfd/readthedocs.org,rtfd/readthedocs.org,rtfd/readthedocs.org