cb = function cb(response) {
      // Does not currently handle Inquirer validation errors.
      resolve(response);
      if (userCallback) {
        userCallback(response);
      }
    }
For use in vorpal API commands, sends
a prompt command downstream to the local
terminal. Executes a prompt and returns
the response upstream to the API command.

@param {Object} options
@param {Function} userCallback
@return {Vorpal}
@api public