feat(router): introduce router (proxy) component into Deis

closes #610 and closes #508. This component will act as a reverse proxy for all Deis components. At the moment, this happens to be just the controller, but functionality to proxy requests cluster-wide for other potentially public-facing components (maybe the registry?) is technically possible to set up.

Router integration with Deis will be in a separate PR (i.e. proxying requests from port 80 to port 8000 on the controller), so that we can handle with pulling the trusted build from the public index.

# Usage

After provisioning a vagrant box:

```
$ sudo apt-get install -yq redis-server
$ redis-cli
127.0.0.1:6349> SET deis-controller.local "10.0.2.15:8000"
127.0.0.1:6349> exit
$ cd /vagrant/router
$ sudo make build
$ export ETCD=10.0.2.15:4001
$ export HOST=10.0.2.15
$ sudo -E make run
```

After waiting for a couple seconds for the service to come up, you should be able to go to http://deis-controller.local/ and see the controller running on the server.