Move to optimist arguments, add support for handoff restarts

* To support handoffs, the launched code must be a Node.js app, and must go
  into a "handoff mode" when sent USR2.  Lifeguard will proxy messages between
  old and new instances, and allow the old one to shut itself down.
Clean up translated handles after handoff

* Solves a condition where lifeguard remains a listening process for the
  sockets that went through handoff. That led to random incoming connections
  getting lost.
Merge pull request #1 from StreamMachine/master

Move to Proper Arguments; Add Handoff Restarts