Set up for Sphinx documentation

Includes additions from output of
  sphinx-autodoc -o docs ../buildapi
rtfd-requirements contains the items needed in the virtual environment
on read the docs to build the docs.
Bug 630633: Option to rebuild N times. r=dustin

Also, change labels for changing priority to make it clearer how to make stuff happen sooner or later.

Allow rebuilding of pending requests as well.
Bug 630633: Bump version to 0.3.0