Can not work with `django-otp` 0.7.0

[Michael Yin]

django-otp now released 0.7.0, it starts to using the latest middleware syntax.

So the old super().process_request(request) can not work because the method does not exist in _OTPMiddleware any more.

I suggest to add notes to README and release a new version to work with django-otp 0.7.0

You can check code here https://github.com/django-otp/django-otp/blob/master/src/django_otp/middleware.py

[Michiel Bijland]

This should already be solved but we are going to pin to 0.7.4 + in #32