Unenforce manual get_context_data()

[James Pic]

Currently, TemplateView inherits render_to_response(context) from TemplateResponseMixin which requires a context argument.

Instead, TemplateView should have its own render_to_response(context=None) that would get a context by default from get_context_data().

TemplateView.render_to_response() should call its ContextMixin.get_context_data() method automatically is because TemplateView inherits from both TemplateResponseMixin, and ContextMixin which provides the get_context_data() method.

Currently, the workaround is to call TemplateResponse.get(request, *args, kwargs), but users should really be calling what they mean to do instead: super().render_to_response()