Force node to start interactively even with no tty
nexpect now requires stable node ~0.10

It used to claim to support node >= 0.2. I don't know how true that was,
but it definitely didn't support node 0.10
Fix wait tests by having test fixture exit

I don't know why prompt-and-respond doesn't exit when run as a child
process, but does when run at the command line, and I don't care right
now, the tests now pass.
Return exit code, or signal if it was killed
Export API documentation from code to README