Add support for listening to all targets of a Notification
Add support for listening to all targets of a Notification

Previously, when the target was nil, the listener would only be
triggered if the Notification had no target.

Now, the listener will be triggered for every Notification,
regardless of its target.

This is more in line with NSNotificationCenter's behavior.

aleclarson/emitter-kit,aleclarson/emitter-kit