Ctrl+C / SIGINT should quit process cleanly

[mjp0]

I have been getting familiar with fbp-spec and I have noticed that for some reason the process doesn't exit properly. It just hangs and my only option is to killall node.

It looks like something is hijacking SIGINT in fbp-spec (at least on macOS 10.12) because I can't CTRL+C out of the process either.

Same problem happens with noflo-nodejs.

edit This could be related to error handling as outlined in #137 because I noticed that my test had a broken fixture syntax thanks to auto-indent so now it works and exits properly.

[jonnor]

Probably need to add an explicit signal handler, and to call cleanup of runtime subprocess