Refs #299: Fix doc for RapidTest

Use Sphinx autodoc to get the right docs for RapidTest, except
for `disable_phases` which Sphinx couldn't find the doc for,
and `apps` which is kind of a fake attribute that only exists
if the user creates it, so there's not even a place to give
it a doc string.

Branch: bug/299-testing-docs
Merge branch 'release-0.12.0' into bug/299-testing-docs

Conflicts:
	docs/conf.py

Branch: bug/299-testing-docs
Refs #299: Respond to review comments

Branch: bug/299-testing-docs
Merge pull request #299 from rapidsms/bug/299-testing-docs

Testing Docs