Merge pull request #9 from cubejs/cluster3

rebase
updates after nodesummit, added uvmon to heartbeat, using process.cluster2 to make sure single cluster emitter/status/cache usage across the whole process, added successorGuard etc.
Merge branch 'cluster3' of https://github.com/inexplicable/cubejs-cluster2 into cluster3
fix multiple instances in a single process
Merge pull request #69 from inexplicable/cluster3

Cluster3