grunt error: cannot find module 'load-grunt-tasks'
Try running:
$ npm install
After that, if you run it and the error still persists or if there's another one, then you probably have not installed ruby, compass or both :)
I had the same issue, the problem for me was in my package.json where I didn't actually install the NPM package needed and it was not automatically installed as previously thought. Try doing
npm install --save-dev load-grunt-tasks
If that doesn't work can you provide the package.json file as well so we can get a little more information.