Adds native Backbone event handling

[snurra]

Here's what expected:

1. Every event is triggered on its model/collection as normal.
2. Every event on a relation is also triggered on its parent as :.
3. Change events are triggered when all setting is completed.
4. There should only be (at most) one single change event on a relational model.

This is meant to mimic how events on a standard Backbone model are triggered.

Fixes #8
Fixes #7 (as an
automatic side-effect, doing it otherwise would be complicated)

[martinlissmyr]

I made this: #10 (could come in handy here I guess).