code: function writeFile(config, isJson, callback) {
    try {
      fs.writeFile('./.nplintrc', isJson ? JSON.stringify(config, null, 4) : yaml.safeDump(config), callback);
    } catch (e) {
      return callback(e);
    }
  }
docs: Create .nplintrc file in the current working directory
  @param {object} config object that contains user's answers
  @param {bool} isJson should config file be json or yaml
  @param {function} callback function to call once the file is written.
  @returns {void}