* Add initial support for Gulp
* Implement clean task to match Grunt behaviour
* Copy from Gulp implementation in Web Starter Kit 0.6.4
* Implement sass task using Gulp
* Implement vulcanize task using Gulp
* Implement Gulp task to minify scripts
* Simplify the Gulp vulcanize task
* Implement Gulp default task to match Grunt behaviour
* Change to use Gulp for build/post install
* Cleanup obsolete Grunt tasks and config
* Grunt is still used for serve task (for now)
* Remove unused Gulp tasks
* Clean up tasks that are not needed, which were copied from
the Web Starter Kit
* Leaving the service worker tasks, as expect those to be used
* Address comments
* Address more comments
* Enable autoprefixer for CSS
* Remove unused tasks