Establish an automated build via Grunt and additional plugins, 3rd party scripts are managed with Twitter Bower.

* Remove all 3rd party scripts from the repository.
* Update Modernizr to a perfectly lean build thanks to grunt-modernizr.
* Refine Sass partials: split `_modules.sass` to dedicated partials for following, likes, notes, pagination.
* Phase out H5BP CSS - what we need is now contained within the `_basics.sass` partial.
* Various smaller improvements and cleanup along the way.

CSS uncompressed for now.
Add CSS minification, update devDependencies.
Merge branch 'feature/grunt-and-bower' into develop