Support CouchDB _updates

[gijohnson-usgs]

I think it would be very useful to support the use of CouchDB update handlers.

Comments in the code:

# jquery.couch.js uses the same method for updating as it uses for creating a document, so we can use the `create` method here. ###
  update : (model, opts) ->
    @create(model, opts)

but jquery.couch.js has db.updateDoc. It's purpose is to execute update handlers.

[gijohnson-usgs]

I see that I'm using Dale Harvey's version of jquery.couch.js which appears to be forked from Apache.

https://github.com/daleharvey/jquery.couch.js.git

[Jan Monschke]

So the orginal one does not have this method?

[gijohnson-usgs]

Doesn't appear so. I realized that I got Dale's version b/c I was using kanso.