added ping interface to channels and fixed tests

broadcast/utils_test.go

channels/adminListener.go

channels/adminListener_test.go

channels/eventModel.go

channels/eventModel_test.go

channels/interface.go

channels/joinedChannel.go

channels/joinedChannel_test.go

channels/messages_test.go

channels/processorList_test.go

channels/send.go

channels/sendTracker.go

channels/sendTracker_test.go

channels/send_test.go

channels/userListener.go

channels/userListener_test.go