Update to use new exec-alternative API

[nfischer]

To eliminate all security holes and get a consistent cross-platform API, this should migrate to ShellJS's exec-replacement after the next release (implementation can start once it has been merged).

[nfischer]

Blocked by shelljs/shelljs#524

[jhenry9636]

@nfischer Sounds like you been working hard. Just wanted to check in to see where you are with this. Can't thank you enough for the fix.

[nfischer]

@jhenry9636 thanks for pinging the thread. I'm still hacking out a prototype, but will ping the linked PR once I have something working a bit better.

In terms of this project, switching to the new API (once available) should be pretty easy.