Fixes incorrect response

[vatson]

No description provided.

[paulbjensen]

I'd be tempted to recommend setting a local variable err with the value null as the first line of the square function, so that the order and context of the response items is clear, e.g.

    squareNumber: function(number) {
      var err, result = null, null;
      typeof number !== 'number' ? err = 'Must be a number' : result = number * number;
      res(err, result);

[davisford]

Looks good to me :)

[paulbjensen]

I'm going to close the issue. Thank you @vatson for taking the time to fork the repo and make a PR, I'm sorry we didn't make use of it this time.