also can we add an option like the example below,

```php
$app->register(new PimpleAwareEventDispatcherServiceProvider, array(
    'pimple_aware_dispatcher.override' => true
));
```
and if override is true we can override `dispatcher` and also provide `pimple_aware_dispatcher` 
else we don't override the original dispatcher but provide only `pimple_aware_dispatcher`

thoughts?