Nyaggle

- Support multiclass classification
- Integrate LightGBM Tuner in Optuna
- Add new ValidationSplitter
- Add feature store module
- Refactor API & various bug fix

- Change license to MIT
- Add example code for [Kaggle Days Tokyo offline competition](https://www.kaggle.com/c/kaggle-days-tokyo)
- Make API more consistent across modules
- Add hyperparameter zoo
- Add TimeSeriesSplit and SlidingWindowSplit splitters for time-series validation

- bug fix
- mlflow integration
- rename modules & functions (cv -> cross_validate, model -> validation)
- adversarial validation
- partial evaluation in cross_validate

- Support CatBoost in experiment module
- Implement averaging
- Various bug fix