PR 26 and 27

[Stéfan van der Walt]

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