Sphinx autodoc and pg8000-1.10.0

In pg8000 we've got the problem that docs are duplicated in the code and the documentation pages. We're using Sphinx, so my plan is to use autodoc, which will pull docstrings from the Python code into the documentation pages.

Right, I've done that. It worked okay, the only wrinkle was that I had to include the docs for instance variables in the overall class docs.

Btw, I've just released pg8000-1.10.0, which includes the release notes.