[Catalog-sig] Recent PyPI changes

["Martin v. Löwis"]

We (Richard Jones and me) made a number of changes to PyPI:
- there is now a way to request release information in JSON,
  see http://tinyurl.com/38lefsp
- it's possible to run the code base locally using sqlite,
  see the README.
- there is now demodata available (see README); people won't
  need a full database dump anymore to develop on the code.

In addition, pypi.appspot.com is likely to become mirror E
(perhaps B instead, so that E can have an A record).

Regards,
Martin