[Reviewer: Andy] Check that ralf is responding and abort it if not

Andy,

Please can you review my fix to make monit check that ralf is responding and abort it if not?  I've manually live-tested, both that it's stable normally, but also that it aborts and restarts if I send it a SIGSTOP (followed by a SIGCONT once the health-checks have failed).

Thanks,

Matt

(fixes #57)
I assume this is a copy of `poll_homestead.sh` with `s/homestead/ralf/g`?