Ratchet does not clearly indicate need for elevated privilege

[msakrejda]

Ratchet needs to run as the user that is running the Postgres cluster. If started as an unprivileged user, it gives an unrelated and seemingly incorrect error:

heroku@1.2.3.4:/tmp/ratchet$ ./ratchet nap --port=5432 15
Could not resolve port None to a PID

Ideally, this should give an error regarding insufficient permissions.

[fdr]

root user is also an acceptable one here, although in general least-privilege seems the best.

I think a 'hint' message may be best, but also it is possible to determine for ports > 1024 if they are bound or not (at the very least, one could just call listen(). In that case, the hint can be even more detailed ("the port is taken, but I can't figure out the pid, are you sure you are using a user with the right perms?")

[fdr]

Changes submitted in c57b6b9