[Cython] Documentation link broken

[Jim Kleckner]

Robert Bradshaw wrote:
> Thanks for the note--looks like he renamed the file. I just fixed it.

This front page duplicates the wiki front page and is subject to divergence:
  ( compare http://www.cython.org/ with http://wiki.cython.org/Cython )

It would probably be better to concentrate on one or the other rather
than keeping both consistent and choosing the wiki page means that
others can fix it when they see it as well.