QA

Fix: not passing form_class

Fix readme

Merge branch 'dicts' into 'master'

Rewrite formfield, callbacks must now return dicts

See merge request oss/djhacker!2

Release for Python 3.7

Merge branch 'jpic' into 'master'

Pass kwargs to callbacks and support re-registration

See merge request oss/djhacker!1

Fix ci