Use websockets to push item/dungeon/location states to browsers

[jhelwig]

Instead of polling from the browser, we should be opening a websocket from the browser, and pushing state back to the browser(s) over it. Ideally, this would re-use the same port that Rocket is already using (but might not be doable until rwf2/Rocket#90 happens).

[jhelwig]

Need to figure out how to hook together Rocket (the current web framework), and rust-websocket. https://github.com/cyderize/rust-websocket/issues/46 looks like a useful place to start looking.

[jhelwig]

Done in bc93b56