Broadcasting mode for instructors

Hi @drio

(refs #3)

I worked on broadcasting mode a little bit.
Thanks to PeerJS "one way calls" it was possible to make this broadcasting mode. However, I'm very unhappy with how events are propagated through Pitt and I really want to drop socket.io and to switch to [WAMP](http://wamp.ws/).

I wrote a [blogpost](http://piotr.banaszkiewicz.org/blog/2014/06/14/peer-instruction-update-3/) about the changes.

There are some bugs in the code, unfortunately. And lots and lots of `console.log` debugging debris.

Some one the bugs include:

* for the broadcasting mode to work instructor have to "show up" last - ie. after all their students show up. That's because the code for instructor emits an event that's crucial for broadcasting when the instructor loads their page.

* after broadcasting session is over, students have to reload their pages in order to receive a new broadcast. Otherwise there's and error occurring in PeerJS lib. I think it's connected to some HTML tag missing from the DOM, but I didn't investigate further.