Fixed #179

Turns out you need to use a promise to ensure that the notification for status is sent *before* the ticket has been closed (if stay on ticket is not selected)
added a promise that should still succeed even if the network request fails, if network request fails the notification will not be sent.

Risks:
Low Risk (3/10), High Impact (10/10):
May break save hook if :assignee.id() == currentUser || !preventAssignOOO
worst case: saving may fail for all tickets where user is assignee, or all tickets if !preventAssignOOO. 
most likely negative impact: increase in latency for saving tickets