Introduction
TODO
http://blog.scottlowe.org/2014/08/01/a-quick-introduction-to-coreos/
https://coreos.com/etcd/docs/latest/getting-started-with-etcd.html
http://blog.scottlowe.org/2014/08/18/coreos-continued-etcd/
http://tdeheurles.github.io/Exploring-etcd/
https://www.digitalocean.com/community/tutorials/how-to-use-etcdctl-and-etcd-coreos-s-distributed-key-value-store