Running repair steps in parallel and minor changes

I think that would be the right way to go here as well.  But I think we should be careful since spinning up 50 processes or even 50 threads could easily DoS a machine.  So we'd probably want to set a more sane default if we were to take that approach.

On that note, I think the way to go here is to use multi-processing. Given that we are subject to the GIL if we use multi-threading, having a few processes makes more sense.  Perhaps we start with something like ` $n cores` processes since they share the machine with Cassandra.