Add a check to detect data uris in Utils.load

Currently Utils.load does not detect data uris correctly. This prevents me from adding an image to a sprite when using data uris.

`sprite.setImage('data:image/gif;base64,R0lGODlhAQABAPAAAP8AAP///yH5BAAAAAAALAAAAAABAAEAAAICRAEAOw==', 10, 10);`