new hg.python.org server

I just switched hg.python.org from a OSUOSL VM to a Rackspace VM. The
new VM is a bit beefier and has what I think is better network
connectivity, so hopefully that will improving the speed of repository
operations. We also now support HTTPS for repository browsing and
cloning, so update all your links to https://hg.python.org! IPv6 support
has also returned for those who like that sort of thing.

Note the host keys changed, so you'll probably have to futz with
known_hosts to quiet ssh down. I apologize, but I noticed that that the
current RSA host key is 1024 bits, so I decided to upgrade it to 2048
during the transition.

Thanks to Donald Stufft for helping me set this up.