Fklearn

- **Enhancement**
- Add verbose method to `validator` and `parallel_validator`
- Add column_duplicator decorator to value_mapper
- *Bug Fix*
- Fix Spatial LC check
- Fix circleci

- **Enhancement**
- Now transformers can create a new column instead of replace the input
- **Bug Fix**
- Make requirements more flexible to cover the latest releases
- split_evaluator_extractor now supports eval_name parameter
- Fixed `drop_first_column` behaviour in onehot categorizer
- **New**
- Add learner to calibrate predictions based on a fairness metric
- **Documentation**
- Fixed docstrings for `reverse_time_learning_curve_splitter` and `feature_importance_backward_selection`

- **Enhancement**
- Now Catboost learner is pickable

- **Enhancement**
- Improve `space_time_split_dataset` performance

- **Enhancement**
- Allow users to inform a Placeholder value in imputer learner
- **New**
- Add Normalized Discount Cumulative Gain evaluator
- **Bug Fix**
- Fix some sklearn related warnings
- Fix get_recovery logic in make_confounded_data method
- **Documentation**
- Add target_categorizer documentation

- **Enhancement**
- Allow users to set a gap between training and holdout in time splitters
- Raise Errors instead of use asserts
- **New**
- Support pipelines with duplicated learners
- Add stratified split method
- **Bug Fix**
- Fix space_time_split holdout
- Fix compatibility with newer shap version