Add grunt support and fix some jshint issues

Maybe you'll want to have a look..

This _PR_ adds a Gruntfile.js with some basic tasks including:
  * hinting of files based on rules defined in `.jshintrc`
  * linting of `.json` files in tests

and also includes fixed `jsint` warnings:
  * fix "Strings must use singlequote" 
  * fix "Bad line breaking before .."

After an `$ npm install ` simply run `$ grunt` ..
we'll probably not need uglify, will we?