The Djblets documentation can now be built with Python 3, providing

better compatibility with our documentation hosting.
This mostly involves changing the version used to invoke Sphinx,

fixing a couple syntax errors (Unicode string prefixes), and removing

the hard-coded python in the Makefiles.
The copyright for the release notes has also been fixed to include

"2009-<now>", and an old reference to "Christian Hammond" as an author

was changed to "Beanbag, Inc."

Successfully built all the documentation.