Bug: EventManager class, attachAggregatemethod expects second parameter to be $priority.

If $event to attach() method was passed as instance of ListenerAggregateInterface, it will be passed to:

$this->attachAggregate($event, $callback); //where second parameter $callback.

But function reads second parameter to be $priority:

public function attachAggregate(ListenerAggregateInterface $aggregate, $priority = 1)

Fix attached.