* Add narrative chapter on initialization
* Be more explicit about defining validators both ways
* Stress that the name of default/validator != attr name
* Mention nested schemas
* Explain handling of private attributes
* Add another consequence of _ stripping
* Stress that nothing should overwrite attributes on class body
* Better wording
* typo
* Dedup examples
* Address review feedback
* Add newsfragments
Pavel Karateev