Basic HTML UI for monitoring Barge cluster

Provides a basic HTML interface to a running demo Barge cluster (URIs are hardwired). The interface is very basic:
* Each replica is a box displaying a "connect" button and a table of events (latest 15, most recent first w/ coalescing for identical events)
* User can connect/disconnect
* Events are fetched through a Websocket interface exposed by Barge's Jetty server

This is mostly for demo purpose right now but I plan to make it more general by exposing Configuration so that display can be built dynamically. 

Some details and shortcomings:
* UI is built using clojurescript + om
* There are no tests for the UI, because I still have to find a way to test it!
* barge-ui project is not integrated in the build