Make sure PIXI is available when using require for phaser builds

This is a hackish solution, and would not be needed if Phaser used require and a JS bundler like webpack

Author: mkristo

src/pixi/Intro.js

@@ -2,6 +2,6 @@
  * @author Mat Groves http://matgroves.com/ @Doormat23
  */
 
-(function(){
+var PIXI = (function(){
 
     var root = this;

src/pixi/Outro.js

@@ -12,4 +12,6 @@
     } else {
         root.PIXI = PIXI;
     }
+
+    return PIXI;
 }).call(this);