Rearrange and comment CollectionView
Make the emptyView management functions private
Fully test View's events
Use a separate event prefix for emptyView
Add trigger() function

To be added to subclasses, or even on Backbone.Events. When `event`
triggers, it will attempt to call `#onEvent`.

- `event` -> `#onEvent`
- `event:type` -> `#onEventType`
- `event:type:sub` -> `#onEventTypeSub`