Use Grunt for the build process

Using @pedrocorreia's branch.

The idea is to normalize and centralize the build process of both CSS/LESS and JS module files using grunt and to leverage third party goodies that come with it.

Also the folder structure is much more simplified. The src folder contains the latest separate less and js modules, while the dist folder contains the bundled, minified and processed versions of JS and CSS as well as some documentation and a few other stuff. 

Maybe we can move both the cookbook and presskit folders up to the root of the project and remove the img folder (why do we use it for?)

The inkjs-old folder contains the legacy remains of the ink-js repository, old samples, tests and build tools for the JS files and modules.