Django-flexquery

Added
* Added Django 3.0 compatibility.
Removed
* Removed Django 2.0 and 2.1 compatibility. These are EOL.

Added
* `UserBasedFlexQuery` can now be configured to handle anonymous users like no user.

Added
* `FlexQuery.from_func` can now set additional attributes on the newly created type
Changed
* Renamed `contrib.for_user` to `contrib.user_based`
* Made the behavior of `UserBasedFlexQuery` when no user was given configurable

Added
* Added `django_flexquery.contrib.for_user.ForUserFlexQuery`
Changed
* Changed directory structure of unittests
* Renamed ``FlexQuery.from_q`` to ``from_func``
* ``FlexQuery`` super-types (those without function attached) don't have a custom
metaclass anymore. This has no effect on the API.

Added
* Added `FlexQuery.call_bound()` method as a hook to preprocess custom arguments.
Changed
* Significantly simplified API:
It's straightforward to build a Q function that produces a sub-query, hence
`FlexQuery` types can now only be created from Q functions, simplifying both code
and unittests a lot.
* Custom functions now get the base QuerySet as first argument.

Added
* Initial release