ref(scheduler): replace announcer with deis/publisher

This has been refactored into a micro-service image called publisher,
which listens on a socket and publishes metadata to etcd.

Note that I pushed my own build of this image as `bacongobbler/publisher`, so before we merge this I'd need to amend the commit and to publish the release as `deis/publisher`. Let me know what you guys think!

Source can be found at https://github.com/deis/publisher