Clean-css-standalone is (obviously) a standalone version of clean-css CSS minifier.
All you need to do is to grab clean-css.js file and put it somewhere in your project. The only dependency is Node.js itself.
node path/to/clean-css.js
See the clean-css repository for examples (remember to always replace 'cleancss' with 'node clean-css.js').
Clean-css-standalone are released under the MIT License.