Code in docs does not produce specified data.#52

In the documentation, the first example demonstrates initialising an `EventForm` instance with some example data (`json`). The next section, "Using patch_data" shows some data which it states is from the first example: ``` >>> form.data { 'name': 'First Event', 'is_public': False, 'location': { 'name': 'some location', 'address': None } } ``` but running the code from the first example produces: `{'name': 'First Event', 'is_public': False}` The `LocationForm` defined in the first example needs to be included in `EventForm` as a `FormField` to produce the data shown in the "Using patch_data" section.