code: function csvWrapForExcel(encoder) {
    // Pipe the CSV encoder to the ucs2 converter
    var converter = new Stream.Transform();
    var csvStream = new Stream.PassThrough();
    converter._transform = function(chunk, encoding, cb) {
      this.push(new Buffer(chunk.toString(), 'ucs2'));
      cb();
    };
    // Write the UCS2 BOM http://www.unicode.org/faq/utf_bom.html#bom1
    csvStream.write(new Buffer([0xFF, 0xFE]));
    return encoder.pipe(converter).pipe(csvStream);
  }
docs: X-Platform Excel encoder