#13 doesn't check python/pyxml version

[Vinod Kurup]

I see that this was mentioned in a egroup message, but
i didn't see a bug logged.

I initially tried peerkat on my system with python
1.5.2 and without pyxml installed. the installation
worked, but feeds didn't show up and i couldn't add feeds.

peerkat should complain if either python < 1.6 or pyxml
absent.

Thanks!