Fklearn

- **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

- **Enhancement**
- Increasing isotonic calibration regression by adding upper and lower bounds.

- **Enhancement**
- Improve split evaluator to avoid unexpected errors
- **New**
- Now users can install only the set of requirements they need
- Add Target encoding learner
- Add PR AUC and rename AUC evaluator to ROC AUC
- **Bug Fix**
- Fix bug with space_time_split_dataset fn
- **Documentation**
- Update space time split DOCSTRING to match the actual behaviour
- Add more tutorials(Pydata)