Enable Gulp.js usage

Some simple instructions to get gulp up and running:

1. npm install gulp -g (global installation)
2. cd ~/project-folder
3. npm install gulp --save-dev (local installation in project folder)
4. npm install gulp-ruby-sass gulp-autoprefixer gulp-minify-css gulp-jshint gulp-concat gulp-uglify gulp-imagemin gulp-clean gulp-notify gulp-rename gulp-livereload tiny-lr gulp-cache --save-dev (local installation in project folder)