+act #13004 Adding TailChopping router

Initial implementation + test for #13004
Does it look ok, or some generalisation with ScatterGatherFirstCompletedRouter should be made instead? 
I will update doc when final solution will appear.
suggestion:

    val cancellables = shuffled map { r =>
       scheduler.schedule(delay, interval) {
         r match {
           case ActorRefRoutee(ref) ⇒
             promise.tryCompleteWith(ref.ask(message))
           case ActorSelectionRoutee(sel) ⇒
             promise.tryCompleteWith(sel.ask(message))
           case _ ⇒
         }