Use childprocess and sys-proctables gems for more robust starting/stopping

The idea is to let the `childprocess` and `sys-proctables` gems do the heavy lifting when it comes to starting process and figuring out which process to kill on stop. I'm running go1.2, but I'm assuming that go1.0/go1.1 still have the relevant process (whether it be `a.out` or the new naming convention) as a child of the `go run` command.