Alternative implementation of entity events

Alternative implementation for #333.

After playing with it I find that I really prefer this method much better. It mirrors the traditional backbone events hash as the 'selector' is re-purposed to mean event target. It also works with declarative binding to `not_a_model_or_a_collection`.

An example would be ...

```coffeescript
listen:
  '!router:changeURL': 'aHandler'
  'change model': 'bHandler'
```

.. instead of:

```coffeescript
mediatorEvents:
  '!router:changeURL': 'aHandler'

modelEvents:
  'change': 'bHandler'
```

Discuss.