code: function createTokenFile(token, tokenFile) {
    return new Promise((resolve, reject) => {
      fs.writeFile(tokenFile, token, (err) => {
        if (err) {
          reject(err);
        }
        resolve(token);
      });
    });
  }
docs: Write a token to a given file.
  @param  {String} token     The token to save to a file
  @param  {String} tokenFile Name of the file to create
  @return {Promise}          Resolves back the token that was passed in