trigger an event when the animation has been finished

This is very useful when using animated-outlet on mobile device. , like mentioned in https://github.com/billysbilling/ember-animated-outlet/issues/28 #28 - you can e.g. trigger a customer redraw like this

```
$('body').on('animated-outlet.animation-finished', function(newView){
                                var $var = $('#main-content');
                                $var.hide();
                                $var.get(0).offsetHeight;
                                $var.show();
                                $var.get(0).style.webkitTransform = 'scale(1)';
});
```

To be dicussed:
 - alternatives to this approach?
 - event-name (namespaced?)
 - event-trigger container ( is there a better place then body to start bubbling the event?


Please dont mind the code-styles - i will fix those after the dicussion, this was just a quick "vim go"