Add support for SkyDNS2.

Ok, this is NON WORKING, but:

* The functions in `skydns.go` to actually access an etcd instance are empty, but trivial to create
* The function `removeService` now only takes an `uuid`, but it should prolly also take an event.Image so that the whole service.Key can be restored. This is the main issue to do be done and I'm not sure if this is the way forward
* Tests are fubar and need `etcd` up and running anyway
* Docs are not updated.