(#2275) - Fix ribbon overflow
(#2190) - new page about adapters

This adds a page that explains all about
the various backends and how you can use
them in different environments.
(#2289) - document "uptodate" event

Based on discussion in #2285, it seems
we mis-documented this as the 'complete'
event, which actually never fires.
(#2281) - test against pouchdb-server
(nick-thompson/express-pouchdb#42) - fix metadata.id

So don't ask me why, but occasionally metadata
is undefined here, so this throws an error in
PouchDB server when you run npm test against it.
Related to #2282.