Integrate Pusher for updates #23
Description
It's really irritating to have to walk around and refresh the display using the keyboard after changing out the tap. We can't do the simple timed auto-refresh any more, now that free Heroku servers only offer 12 hours of uptime a day.
However, we can have our back end push updates to Pusher, and have a free Pusher service push those updates to our kiosk view via a Pusher websocket. Even if that pusher update simply did a refresh of the page, it's better than nothing and wouldn't require changes to our Heroku setup.