Handle roster messages

ACE-42
Removed handling of missed messages since sockJs takes care of it
Merge branch 'createRosterAddedController_ACE-44' of github.com:ualerts-org/ualerts-chat into createRosterAddedController_ACE-44
Implement Michael's Callback object for adding listener callbacks.

ACE-42
Merge pull request #15 from ualerts-org/createRosterAddedController_ACE-44

Create roster added controller ace 44