0.9 devel documentation update

These are the doc changes to highlight the changes between 0.9.4 and 0.9.5.

I'd like to shoot for a very simplistic and readable doc generated by Sphinx (I've chosen the built-in "pyramid" theme). If we're happy with the outcome, I'm going to start packaging the 0.9.5 release and checking in the generated HTML to the repo (and the website) too.