Track attached events

You can now detach the listener with the detach() function, as per
ListenerAggregateInterface.
Signed-off-by: Michael Gooden <michael@bluepointweb.com>
Merge branch 'hotfix/8'

Close #8
Merge pull request #10 from MichaelGooden/hotfix/api-problem-listener-events

Track attached events
Merge branch 'hotfix/10' into develop

Forward port #10