WIP - fixed chat in cluster

Pulled in strong-cluster-socket.io-store and modified bin/cluster and
lib/worker.js to configure socket.io with this store.

Work in progress - we need to update package.json to use strong-cluster-socket.io-store from npm.

@Schoonology or @sam-github: please review ASAP, needs to be merged by Monday before the code-freeze for 1.1.