code: function applyLayout(chunk) {
      chunk.data.contents = String(chunk.contents);
      var layout = getLayout(chunk.data.layout),
          contents = options.renderTemplate(layout.contents, chunk.data, layout.path);
      chunk.contents = new Buffer(contents);
      return chunk;
    }
docs: set chunk contents as template data property and render it with a layout
  @param  {object} chunk stream chunk object
  @return {object}       chunk with applied layout