Replace Paramiko with sshpass

Using Paramiko has caused us nothing but pain, and we were only using it because we didn't have a way to pass a password to the ssh command. The sshpass package is tiny and widely available. The tradeoff here in terms of performance is that we're giving up the overhead of a massive SSH library that we only used a fraction of, for the overhead of shelling out more. I'm okay with that.

@herlo, @seanchannel and @cedwards will want to be aware that we have removed paramiko as a dependency, and added sshpass. I've been able to find it in epel, packages.debian.org, packages.ubuntu,org and even in the Arch community repo.