Added option for fields in TheForm superclass

Using the latest version of django (1.8), I was getting a ModelForm error whenever I used ```make_ajax_form```. Turns out that it is now a requirement for the fields attribute (or exclude) to be included when creating a form, [according to the docs](https://docs.djangoproject.com/en/dev/topics/forms/modelforms/). Adding ```__all__``` seemed to resolve the issue.