New features:
- Optimal binning 2D support to categorical variables for binary and continuous target.
Improvements
- Integer intercept if ``rounding=True`` 165.
- Parameter ``show_digits`` applies to scorecard table bin column 170.
Bugfixes
- Fix ``Scorecard.score`` method when there are special and missing bins 179.
- Fix x and y axis labels in ``OptimalBinning2D`` plots, x and y were interchanged.