Owlmixin

Bug fix
- :skull: Fix that some `from_optional_xxx` methods don't returns value as expected

New features
- 🆕 Add support for Enum (please use OwlEnum)

ex.

python
from owlmixin.owlenum import OwlEnum

class Color(OwlEnum):
RED = "red"
GREEN = "green"
BLUE = "blue"

Bug fix
- :skull: Fix `flat_map`

New features
- :new: Add `intersection` and `not_intersection`
- :new: Add `flatten` and `flat_map`

Improvements
- Enhancement the transformation on `force_snake=False`
- `--hogeHoge` => `hoge_hoge`
- `-h` => `h`
- `<hogeHoge>` => `hoge_hoge`

Change architecture

Documentation

API documentation is more readble.

Breaking changes

Because of breaking changes, You need that ...
- Import from `owlmixin.owlcollections` instead of importing from `owlmixin` if you want to import TList or TDict
- Override property `_dict` instead of overriding function `_to_dict()` if you need