An app launched by a GUI launcher (Finder, Dock, Spotlight etc.) receives a pretty empty and useless environment, since standard Unix ways of setting variables via e.g. ~/.profile do not work.
http://stackoverflow.com/questions/135688/setting-environment-variables-in-os-x
So, code exec('node --version' in the check-node.js doesn't work because node cannot be found (if you run app, not electron ., see #17).