Poniard 0.2.1

What's Changed

• Allow adding preprocessing steps to existing preprocessor and add VarianceTreshold by @rxavier in #9
  • Implements add_preprocessing_step
  • Removes transformers with no assigned features from the preprocessor
  • Include a VarianceThreshold transformer at the end of the default preprocessing pipeline
  • Don't use TargetEncoder if the target is multi output, switch to OrdinalEncoder instead
  • Set TargetEncoder to ignore unseen categories - will use the mean of the target
  • Improve TargetEncoder docs
  • Clear the _fitted_estimator_ids after adding a preprocessing step or reassigning types (which triggers a rebuild of the preprocessor)

Full Changelog: 0.2.0...0.2.1