This will make it much easier to fix bugs and make improvements going
forward, since they won't have to wait for the next release of Meteor.
One functional change: when the parent process exits, it no longer forces
all connected shell clients to disconnect, which is actually a more
convenient behavior, because it gives the clients a chance to reconnect
when/if the server starts up again, and it's easy enough to kill the
clients if that's what you want.
