Use autodoc for reference docs

[meatballs]

At the moment, the reference docs are built locally (using a monkey patched autodoc function) and the resulting .rst files are placed in the main docs folder.

Once ReadTheDocs is able to support Python 3.6, we should remove that facility and use autodoc directly within the the docs.

https://github.com/rtfd/readthedocs.org/issues/2584