second set of revisions

All the major sections are now revised and/or written, with the exception of the extensions API.
For the extensions API, I'm likely going to pull text I wrote to the mailinglist, then point the reader at that post for the full details.
Next up I'll be working on the intro.

The remaining sections for review seem to be pretty minor. I might pull in handful of them, but we'll see what we have time for.