Ability to deploy serially

Hello,

Thanks for the simple and great naught lib.

I was wondering if you ever had the need to support serial deploys. Meaning when you do `naught deploy`, workers get replaced one by one, avoiding an unusual load on the machine.

Our use case is, we're limited in RAM, and we have two workers. Those two workers take between 60 to 80% of the RAM. Right now, deploying would mean a heavy use on the RAM, it'd be great if we could smooth the process by replacing processes one after the other.