ctrl-c loses default behavior

The index.js file was overriding the SIGINT event. This was not allowing us to kill the parent process because overriding the SIGINT event removes the default handler (http://nodejs.org/docs/latest/api/process.html#process_signal_events).

The process still listens for the 'exit' event, which gets signaled when calling SIGINT as well. Using that instead to kill child process.