* Get rid of `track` in errors
* Move `display_as_type` func into utils module
* Get rid of error as `namedtuple`
* Renamed `Error.index` to `Error.loc`
* New way to get error type
* New way to get error message
* New errors format
* Renamed `flatten_errors` property to `flat_errors`
* `__slots__` for `Error` and `ValidationError`
* `loc` as `tuple`
* Tests
* Review fixes
* `flatten_errors` as generator
Nikita Grishko