implemented all clusterheartbeat materials
ClusterHeartbeatSenderStateSpec implemented and passes

Also added the ClusterSpecBase class mentioned in the comments for #369
implemented HeartbeatNodeRingSpec
Complete ClusterDaemon and port AutoDown and AutoDownSpec
Merge pull request #2 from smalldave/akka-cluster

Complete ClusterDaemon and port AutoDown and AutoDownSpec
Merge pull request #380 from Aaronontheweb/akka-cluster

ClusterHeartBeat implementation