Fixed tests so that they run properly

However, the result is not a working app. The main thing here is I got the tests running and got rid of warnings. I did this all on Ruby 2.1.3

I had to comment one test out because it couldn't figure out how to build 'pkg' but then when I go to build again, I have to `rm -rf pkg` anyway to get the app to build again.

Hope this helps (and sorry I forgot about the topic branch). Started committing on master before I thought it through.
This might be worth revisiting whether it should return the command or true and false. I've also now based it on both the result of the command and the result of `$?`