Support Backbone.Sync capabilities

Hi,

I've been looking for a good way to use a backbone app with a JSON API. It looks like all that would need to happen for sync support is to override the [Backbone.sync](http://backbonejs.org/docs/backbone.html#section-169) method. I don't know if you've given any thought to this, but if I hacked at a rudimentary solution, would you be interested in a pull request for it?

Thanks!
