code: function s3streamer(s3, opts) {
    var headers = (opts || {}).headers || { }
  
    return function (file, filename, mimetype, encoding, callback) {
      headers['Content-Type'] = mimetype
      var buf = Buffer(0)
      file.on('data', function (chunk) {
        buf = Buffer.concat([buf, chunk])
      })
      file.on('end', function () {
        s3.putBuffer(buf, filename, headers, function (err, s3resp) {
          if (err) {
            return callback(err)
          } else if (s3resp.statusCode < 200 || s3resp.statusCode > 299) {
            return callback(new Error('Error uploading to s3: ' + s3resp.statusCode), s3resp)
          }
          s3resp.resume() // This finalizes the stream response
          callback()
        })
      })
    }
  }
docs: An s3 streamer