small spelling fix
=act #3645 Make TcpOutgoingConnection actor handle UnresolvedAddressExceptions
#3655 clu Stop sending EndHeartbeat after ack
!rem #3646: Optimize sending of Ack messages
Merge pull request #1754 from drewhk/wip-3646-sysmsg-ack-optimization-drewhk

!rem #3646: Optimize sending of Ack messages
Merge pull request #1759 from akka/wip-3655-stop-endheartbeat-patriknw

#3655 clu Stop sending EndHeartbeat after ack
Merge pull request #1732 from luc-at-jr/master

small spelling fix in Slf4jEventHandler.scala
!per #3652 Custom snapshot and persistent message serialization

- Protobuf serializer for Persistent message
- Configurable serializer for Persistent message's payload
- Configurable serializer for snapshots
Merge pull request #1757 from eligosource/wip-3652-custom-serialization-krasserm

!per #3652 Custom snapshot and persistent message serialization
=clu #3660 Simple speedup of gossip in early phase
Merge pull request #1764 from akka/wip-3660-simple-speedup-of-gossip-in-early-phase-ban

=clu #3660 Simple speedup of gossip in early phase
Merge pull request #1752 from spray/wip-3645-handle-UnresolvedAddressExceptions

=act #3645 Make TcpOutgoingConnection actor handle UnresolvedAddressExceptions
=doc #3639 Show complete custom mailbox example.
Merge pull request #1768 from akka/wip-3639-doc-show-producesmessagequeue-ban

(forward port) =doc #3639 Show complete custom mailbox example.
Merge remote-tracking branch: upstream/master