onBeforeSave( info ) {
    if (info.outputFile.endsWith('.css')) {
      return info.mk;
    }
    if (this.opts.prettify) {
    return HTML.prettyPrint(info.mk, this.opts.prettify);
    } else { return info.mk; }
  }
Copy satellite CSS files to the destination and optionally pretty-print
  the HTML resume prior to saving.