[Catalog-sig] Changes to the simple pages

["Martin v. Löwis"]

> No, what I mean is that if PyPI returns *identical* HTML for requests
> going to "/foo" and "/foo/", then one of those pages will contain
> incorrect relative URLs.

Thanks a lot. I probably wouldn't have considered that; now I followed
your suggestion of adding redirects.

I have also changed the content to be well-formed XML.

If somebody encounters a problem, please let me know.

Regards,
Martin