Fix shelljs exec usage, part 2

[airdrummingfool]

Sorry, I missed a couple of places where .output was used.

Ref #30.

[shazron]

I'm going to be adding tests tomorrow, just in case, so we don't have to have part 3 :)

[airdrummingfool]

That's a good idea. I double-checked this time around, but it's always nice to have more checks 😅

[shazron]

merged in the unit tests to this, but now there is a lint error. I'll fix it later and merge this :)

[airdrummingfool]

Thank you!