Replace noSender in DeadLetterActorRef, see #2882
make ActorRefSpec more deterministic, see #2836
Fixed issue with Netty not releasing worker threads properly #2733
Publish InstantMemberEvent immediately, see #2803
Incorparate review comments, see #2803
Merge pull request #1015 from akka/wip-2882-deadletter-null-sender-patriknw

Replace noSender in DeadLetterActorRef, see #2882
Merge pull request #1020 from akka/wip-2836-ActorRefSpec-∂π

make ActorRefSpec more deterministic, see #2836
Merge pull request #1024 from drewhk/wip-2733-netty-workerpool-shutdown-drew

Fixed issue with Netty not releasing worker threads properly #2733
Merge pull request #1025 from akka/wip-2803-instant-member-events-patriknw

Publish InstantMemberEvent immediately, see #2803