Don't specify a hostname for psycopg2 so it uses sockets

If you don't specify a hostname Psycopg2 will use sockets
(passwordless) instead of a TCP connection (requires un/pw) so it "just
works" when run as root (with a standard pg_hba.conf).
Merge pull request #3 from notpeter/master

Remove 'host=localhost' from psycopg2 connect string to force socket connection