Use crossOrigin=true on images to allow getImageData/WebGL

If not using crossOrigin=true, the canvas get "tainted" which throws an exception when you want to use it as a WebGL texture or if using getImageData()

Author: gre

lib/ImageCache.js

@@ -10,6 +10,7 @@ function Img (src) {
  this._img = new Image();
  this._img.onload = this.emit.bind(this, 'load');
  this._img.onerror = this.emit.bind(this, 'error');
+ this._img.crossOrigin = true;
  this._img.src = src;
 
  // The default impl of events emitter will throw on any 'error' event unless