Removed inline JavaScript, added text about unit testing

I have removed the KeysLeftViewModel and getUrlVars functions from index.html to the already added external files (keysleft.js and keysleftviewmodel.js). Added script tags in Index.html for the js files. I also added querystrings to the url:s in the script tags, to prevent browser caching of old versions. The querystrings should be updated when changing the js files.

I have also added a README.md file in the tests folder, containing a short text and intro about unit testing for this project. I also added a link to a 15 minute video I have recorded about TDD for JavaScript.