Ensure that behavior events are bound to the behavior.

According to [the docs](https://github.com/marionettejs/backbone.marionette/blob/master/docs/marionette.behavior.md#using), Behaviors have their events bound to the View:

```
// behaviors have events that are bound to the views DOM
events: {
  "click .close": "warnBeforeClose"
},
```

However, the next function uses a reference to the *Behavior*:

```
warnBeforeClose: function() {
    alert(this.options.message);
    // every Behavior has a hook into the
    // view that it is attached to
    this.view.close();
}
```

If the function is the desired behavior (:smirk:) and events should be bound to the **behavior**, this PR fixes the issue. If not, I can fix up the function in the docs.

FYI - I couldn't update the Behaviors specs. I would have normally used `expect(spy).toHaveBeenCalledOn(behavior)`, but there aren't any references to the Behaviors (that I know of).