Add events when items are added/removed from a queue

It's possible that items were removed even if the queue stayed the same size or new items were added. It would probably be better to compare the original items with the new items, and if any that are in old items are not in new items, dispatch a removed event with those items, and any that are in new items that are not in old items dispatch an added event with those items.

@achap is right, we can't rely on the queue size to determine the changes that happened.