Fix for requirejs via phaser

Fixed compatibility with phaser and requirejs. Seems that phaser uses p2 globally, and when included with requirejs, it fails to pickup the global p2.

Gruntfile.js

@@ -11,7 +11,8 @@ module.exports = function(grunt) {
                 dest : 'build/p2.js',
                 options:{
                     bundleOptions : {
-                        standalone : "p2"
+                        standalone : "p2",
+                        insertGlobals: true
                     }
                 }
             }