master
`master` is now the only permanent branch. Features and fixes should be merged into `master` when stable. Pull requests should be forked from `master`. `develop` branch disappear entirely in favor of temporary features/fixes branches.
Since the release of Read the Docs 2.5 this is no longer required and it broke version selector.
For details, see https://github.com/rtfd/readthedocs.org/issues/1487 FIX #153