Small bug in EGOImageLoader

[mblackwell8]

the keyForURL method returns the hash of the URL description string, which is probably a bad choice. I found examples of URL descriptions that were different but returned the same hash (and if I remember my comp sci well enough, I think this is typical of most hash code implementations).

Better to key the cached UIImage's with the URL's absoluteString, which is working for me so far.