Fix warnings in the documentation build

Some of the docstrings pulled into the API documentation
were malformatted, so fix those. Also include the API
documentation in a toctree so it is linked in the
"Contributing" section of the documentation.

Change-Id: I8eef6007045d5426299dadb67303102855c15dc2
Signed-off-by: Doug Hellmann <doug.hellmann@dreamhost.com>
Merge "Fix warnings in the documentation build"