Grunt -> Eslint + JSHint + Uglify

Hello!

Thank you for accepting my previous pull request. We have a Node.js course and at this moment so we are practicing Grunt.
Because i already pulled to your repository i decided to add Grunt service. It runs JSHint, Eslint and Uglify, I understand that this is not necessary for a so small project like yours but still if you are interested you can accept my pull request.

Best regards
TomTer