++++++++++++++++++
* Add ability to use existing data in form
* DEPRECATED: Any code which previously used `Schema().render(MyForm)` should
now use `Schema().render(MyForm())` (in other words, `render()` accepts an
instance of a form, rather than a form itself). To check if you are calling
the function against contract, you can run your code with `python -Wd`
(e.g. `python -Wd manage.py runserver`).