Node and redis pubsub demo.

The idea here is to be able to share the state of an LED
controlled by gpio pins through a webpage. This doesn't
control the gpio pins, but it does propagate any redis
publish messages to the loaded web pages.
Add a button to the page which sends a new state.

The button just toggles between 'on' and 'off'.

Bugs:

 - Don't get initial state on connect.
 - 'traffic' status message ends up on top of
   the button, or as the button title.
 - server doesn't seem to close websockets
   when the page is closed.
Remove useless #center styling.
Fix outstanding issues with the lamp demo.

Save the current state in redis and send it on connect.
Redis doesn't give the last message to new subscribers,
so this is needed to initialize the button.

Make things more self-referential and clean up logging.

Use an <input type=button> instead of a <button> because
it's simpler to use the value for the display text that way.