If you haven't used Grunt before, be sure to check out the Getting Started guide, as it explains how to create a Gruntfile as well as install and use Grunt plugins. Once you're familiar with that process, you may install this plugin with this command:
npm install grunt-contrib-cssmin --save-dev
Issues with the output should be reported on the clean-css issue tracker.
Run this task with the grunt cssmin command.
Options are passed to clean-css. In addition this task defines some extra options:
Report minification result or both minification and gzip results.
This is useful to see exactly how well clean-css is performing but using 'gzip' will make the task take 5-10x longer to complete. Example output.