code: function concat(app) {
    var files = app.views.files;
    var css = '';
  
    for (var file in files) {
      if ('.css' != path.extname(file)) continue;
      css += files[file].contents.toString();
      delete files[file];
    }
  
    css = myth(css);
    app.files.addView('index.css', {
      contents: new Buffer(css)
    });
  }
docs: Concat plugin.
  
  @param {Object} `app` Assemble instance