Add crossOrigin Anonymous in Konva.Image.fromURL to prevent tainted canvas

See: https://github.com/konvajs/konva/issues/382

src/shapes/Image.js

@@ -239,6 +239,7 @@
       });
       callback(image);
     };
+    img.crossOrigin = "Anonymous";
     img.src = url;
   };
 })();