Staticmodel

- Fix broken 1.1.2 distribution

- Fix incompatibility with Python 3.10

- Fix incompatibility of model fields with newer Django versions.

* Explicit subclassing of 'object' type has been removed.
* Main documentation has been extensively updated to compare against the built-in 'Enum' type.
* Formatting of Django Rest Framework serializer fields documentation has been fixed.
* Version number in documentation has been fixed.

IMPORTANT: This version is not backwards compatible with code using 0.x.
Attempts have been made below to specify potential breaking changes,
but there may be others. You have been warned.
* All support for Python 2 has been removed.
* The django.fields module has been removed. Use django.models.fields instead.
* The members.filter() method now returns all members when called without
criteria.
* Placeholders with a value of None are now inserted in results of
members.values() and members.values_list() when specified fields do not exist
on a member in the results.
* Django Rest Framework serializer fields now require DRF 3.x API.
* Django Rest Framework serializer fields can now serialize the entire static
model member, and handle the corresponding mapping in a representation.
* A members.choices() method has been added as a shortcut for generating 2-item
tuples from static model members.
* Documentation has been updated.

* Add tests for Django Rest Framework serializer fields.
* Fix bugs in Django Rest Framework serializer fields.
* Add DRF version clarification to serializer module docstring.