Broken link in README

[mirkov]

REAME gives a link to a pdf file specifying ropes - the link is broken.

If I have time I will try to find the correct permanent reference, but right now I don't. I could google the pdf file, but I am not sure how stable those links are.

Mirko

[Ramarren]

I have changed the link to citeseer copy which looks the same as my local copy. I don't know how stable that is either, if you find a better reference I will change it.