Update spec/resources/etcd-cluster for latest (v0.1.1) etcd
Outline the advanced features in the readme
Change the leader and cluster discovery

Reflect changes in etcd: the format of the cluster introspection features now includes "http://" and the leader and machine URIs have become versioned.

This doesn't work with the current version of etcd (v0.1.1) since it returns the wrong port for the leader URI (it returns the Raft port, not the Etcd port).
Use :uri instead of :host and :port to connect
Mark integration specs as pending when etcd not running
Run whole test suite in Travis

(the integration tests will be marked as pending when etcd is not running)