This Gruntfile.js will clean your dist folder, concat & minify all js, css assets according config specified in html, put revisions, minify html and copy new folder structure to dist.

Gruntfile.js

module.exports = function(grunt) {

  require('load-grunt-tasks')(grunt);

  grunt.initConfig({
    clean: ['dist'],
    copy: {
      generated: {
        src: 'src/index.html',
        dest: 'dist/index.html'
      }
    },
    filerev: {
      options: {
        encoding: 'utf8',
        algorithm: 'md5',
        length: 20
      },
      source: {
        files: [{
          src: [
            'dist/js/*.js',
            'dist/css/*.css'
          ]
        }]
      }
    },
    useminPrepare: {
      html: 'src/index.html',
      options: {
        dest: 'dist'
      }
    },
    usemin: {
      html: 'dist/index.html',
      options: {
        assetsDirs: ['dist', 'dist/css', 'dist/js', 'css', 'js']
      }
    },
    htmlmin: {
      dist: {
        options: {
          removeComments: true,
          collapseWhitespace: true
        },
        files: {
          'dist/index.html': 'dist/index.html'
        }
      }
    }
  });

  grunt.registerTask('default', [
      'clean',
      'copy:generated',
      'useminPrepare',
      'concat',
      'uglify',
      'cssmin',
      'filerev',
      'usemin',
      'htmlmin'
  ]);
};

package.json

{
  "name": "25-grunt-purifycss",
  "version": "0.0.1",
  "description": "Grunt plugin remove unused css",
  "main": "Gruntfile.js",
  "repository": {
    "type": "git",
    "url": "git://github.com/kanakiyajay/grunt-tasks.git"
  },
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "Jay Kanakiya",
  "license": "ISC",
  "devDependencies": {
    "grunt": "^0.4.5",
    "grunt-contrib-clean": "^0.6.0",
    "grunt-contrib-concat": "^0.5.1",
    "grunt-contrib-copy": "^0.8.0",
    "grunt-contrib-cssmin": "^0.12.3",
    "grunt-contrib-htmlmin": "^0.4.0",
    "grunt-contrib-uglify": "^0.9.1",
    "grunt-filerev": "^2.3.1",
    "grunt-purifycss": "^0.1.0",
    "grunt-usemin": "^3.0.0",
    "load-grunt-tasks": "^3.1.0"
  }
}