PR 26 and 27

Hi all, The radon transform code written by Pieter works well, but currently depends on PIL. I've added "fast_homography" to scikits.image.transform: https://github.com/scikits-image/scikits.image/pull/26 The idea is to eventually replace scikits.image.transform.homography by fast_homography. With the new function in place, the radon transform code can run without using PIL: https://github.com/scikits-image/scikits.image/pull/27 As a bonus, the results are also more accurate, because we don't convert to uint8 afterwards. Please review! We're making good progress to the release; thanks to everyone who has helped out so far. Thanks Stéfan