Feature/router interface refactor

This PR changes Router to an interface, add's registration functions for the server to trigger the router on UAID changes, and a Start/Close scheme for any other things a Router needs to manage.

It also introduces the use of Goconvey and gomock along with most of the mocked interfaces for easier testing.

Closes #127.

@jrconlin, @kitcambridge, r?

If you omit `Addr`, it'll listen on an ephemeral port. The smoke tests use this to avoid collisions, and extract the URL via `router.URL()`.