implement tile movement

js/application.js

@@ -1,4 +1,4 @@
-document.addEventListener("DOMContentLoaded", function () {
-  var actuator = new HTMLActuator;
-  var manager  = new GameManager(4, actuator);
+// Wait till the browser is ready to render the game (avoids glitches)
+window.requestAnimationFrame(function () {
+  var manager = new GameManager(4, KeyboardInputManager, HTMLActuator);
 });