save(stream, dest) {
    return new Promise((resolve, reject) => {
      mkdirp(dirname(dest)).then(() => {
        const file = createWriteStream(dest, { mode: 0o664 });
        stream.pipe(file);
        file.on("finish", () => {
          file.close(resolve);
        }).on("error", reject);
      });
    });
  }
Saves the streamed file to the destination
@param {http.IncomingMessage} stream 
@param {string} dest