Handy

- fixed JSONField and PickleField in Django 1.9+
- fixed Python 3 support in some model fields
- support PyPy
- added pickle param to JSONField
Backwards-incompatible changes:
- JSONField no longer pickles everything non-jsonifyable by default,
set its pickle parameter to True to return this behavior.
- PickleField and JSONField pickles are encoded differently,
so upgrade with old data won't just work.

- unified and updated render_to_json and ajax serialization
- fixed http.pipeline()
Backwards-incompatible changes:
- ajax no longer support .__json__() method or special datetime handling.
It uses Django encoder now.

- fixed render_to_email() in newer Djangos

- fixed JsonField form field in new Djangos

- made JSONField and PickleField work with newer Djangos
- switched to better cached_property implementation

- fixed broken import in Django 1.9