Move master off of 2.4.4

[nicholasphair]

#56 added support for different Sphinx versions through tags. master, however, still points to 2.4.4. That was purposeful. It was done to not immediately breaks builds and give people time to kick the tires on the tagging approach.

This issue is for tracking/coming up with a sane policy for moving the the master pointer to something more recent. Perhaps just a message in the logs encouraging folks to pin a specific version.