cssmin:
  { generated:
   { files:
      [ { dest: 'dist/styles/vendor.css', src: [] },
        { dest: 'dist/styles/main.css',
          src: [ '.tmp/styles/main.css' ] } ] } }

grunt.registerTask('build', [
    'clean:dist',
    'wiredep',
    'useminPrepare',
    'concurrent:dist',
    'autoprefixer',
    'concat',
    'ngmin',
    'copy:dist',
    'cdnify',
    'cssmin',
    'uglify',
    'filerev',
    'usemin',
    'htmlmin'
  ]);