Events: suggestion

Hi,

Events are not described in docs, but from what I see the package fires 3 events:

```
RepositoryEntityCreated
RepositoryEntityDeleted
RepositoryEntityUpdated
```

That is not very comfortable because 1 Listener will listen to all created/deleted/updated events on all the Repositories. Is there a way to specify those events the same way Eloquent Model does:

```
/**
* The event map for the model.
*
* @var array
*/
protected $events = [
'saved' => UserSaved::class,
'deleted' => UserDeleted::class,
];
```

It is more comfortable way as for me, but at the same time it looks a bit like repeating stuff from Eloquent Model. Then is there any sense in including events to the package at all? From the other hand if I use events from Eloquent Model while using l5-repositories then I am losing some kind of abstraction. Sorry If I missed something and thank you for this great package.