One of the loop bindings in move-{left,right} was constant, so
replace that with a let binding (if needed).

* Factor out some common code in end game messages
* Handle the "restart" event so the game can be restarted

The animations are annoying because, as React/Om is taking care
of the DOM updating, tiles are different after moving.

* Make a simplistic implementation of both winning and losing
* This implementation allows the game to continue below the
  overlay, and doesn't have a restart option
* The code is also suboptimal, needs refactoring

Includes a somewhat simplistic implementation of adding a new tile
for every move.

* They're now run with Karma
* The React library is now downloaded and used locally
* The module ttfe.core now has an "init" function that must be
  called from index.html, to avoid that the tests choke when they
  can't "paint" the page