no error/response in callback when trying to add a (i.e) class

[adamwardecki]

In node env:

1. Connect in an account scope:

    const syncano = new Syncano({accountKey: globals.tempAccountKey, baseUrl: 'https://api.syncano.rocks'});

1. Try to add a class:

    syncano.instance('instance').class().add(classOptions, function(err, res) {
      if (err) {console.log(err); return;}
      console.log(res);
    });

Nothing is being logged to the console

Promises work as expected. This code:

    syncano.instance('instance').class().add(classOptions).then(function(res) {
      console.log(res);
    });

logs the response to the console

[kellyjandrews]

There was an error in the helper method checking for the callback functions. I have a fix and will get patch in v0.3.4 right now.