Store old events to apply them again on commit

Hi !

I give a try to your lib and it looks pretty awesome with the last changes.

I just found a problem. You apparently does not keep old events. But you are looking for them here:
https://github.com/beberlei/litecqrs-php/blob/master/src/LiteCQRS/EventStore/OptimisticLocking/OptimisticLockingEventStore.php#L67

So I just add a line to store them.

With this fix I succeeded to make all your stuff working.