code: function markdown(preset, options) {
    var stream = through(transform, flush)
    var parser = new Remarkable(preset, options)
    var buffer = []
  
    function transform(chunk, encoding, done) {
      buffer.push(chunk)
      done()
    }
  
    function flush(done) {
      this.push(parser.render(buffer.join('\n')))
      done()
    }
  
    return stream
  }
docs: Tranform a stream of Markdown into HTML.
  
  @param  {string} [preset]
  @param  {object} [options]
  @return {object}
  
  @api public