jQuery via cdnjs with local fall back and gitignore

I've added `jQuery` and other dependencies to load via cdnjs . 

I am not quite sure if it's a good idea because if you load the file without any web server, this will not work `<script src="//ajax.` . If you can add `http` instead. 

Plus, I've added a `gitignore` file. IMHO, every program with git should have `gitignore` and `README` :+1: