Refactor to use Cuttlefish

The logging output is all completely changed, since Cuttlefish does things in a single big task queue, rather than a bunch of independent steps.

But, I'm seeing about a 10-20% speed increase, once I figured out how to work around joyent/node-manta#152.

If it meets with your approval, you can probably nudge the logging output around easily enough using the events that Cuttlefish gives you.  I'd also recommend adding a flag to enable the `timingDebug` option in Cuttlefish, it's really useful for debugging issues.