* Added `linear_model.Stepwise()` class to perform variable selection for linear models compatible with statsmodels. Contains several improvements and bug fixes over the `linear_model.stepwise` module functions.
* Deprecated `forward_selection()` and `both_selection()` functions from `linear_model.stepwise` models. Added corresponding warnings.
* Modified Getting Started section in Documentation to include the new feature.
* Modified README.md file to include the new feature.