Acknowledge TCP shutdown on ConnectionClosed

Hi,

We are using rediscala and we started encountering an issue with log spam of the following message: `2014-08-05 13:11:49,016	C2	WARN	172.26.15.54	asc-svc-rediscala.rediscala-client-worker-dispatcher-522:akka://asc-svc/user/RedisClientConnection-$zz	:	x1465743556	redis.actors.RedisClientActor	ConnectionClosed PeerClosed`

We tracked down the message origin and figured that possibly the tcpWorker was not being given a confirmation that it's client received the closed connection message and so was continuously sending it back. We added this one liner to rediscala and it fixes the spamming for us. Does this look like a clean fix?