Flag for Animating the setting of images for RZLoadingImageView

@ndonald2 let me know if you think this makes sense.  It seems like we were potentially decompressing already decompressed images, I'm not really sure if this is that large of a performance hit at all but it was at least causing a bit of inconsistency when we thought we were not loading something from the cache when we really were.

Saw the extended file attributes on http://nshipster.com/extended-file-attributes/ a while back and figured this could be an interesting place to try them.

The other feature in the Loading image View to allow the user to control if they want to animate the loading of an image when it gets set.