add 2048 game

public/game2048/js/bind_polyfill.js

@@ -0,0 +1,9 @@
+Function.prototype.bind = Function.prototype.bind || function (target) {
+  var self = this;
+  return function (args) {
+    if (!(args instanceof Array)) {
+      args = [args];
+    }
+    self.apply(target, args);
+  };
+};