Originally, the commands from the controller would be delegated to the
display which computed the game logic. Nowadays the logic is handled on
the server, meaning that the clients do not need to listen to the
command events at all - they only listen for "state" events.

Removed unnecessary socket event listener from withSocket, stuff
related to the old architecture from storybook, and the
SocketIODisplays::sendActions method from the server.

Previously the Display component's socket event type was filtered in
onSocket. Now that the only inbound message is "state", it can be
filtered in componentDidMount.

The previous lazy loading function would cause the first analytics event
to be lost because fn() was never called after ReactGA.intialize.

Instead of directly fixing that, I chose to initialize ReactGA in the
constructor instead.

Instead of checking isBrowser() inside the GoogleAnalytics class, the
_app component now just uses a factory method to create the correct GA
implementation. When in SSR (not in browser), a dummy analytics impl is
used.

Instead of hooking up a sendAnalytics call in render(), the "active view
changed" analytics event is now sent via an observable subscription.