Refactor cv code
Clean up
Refactor RFE and add _check_scorable
FIX typo in docstring
Merge `fit_grid_point` into `_cross_val_score`
Return time
Move set_params back to fit_grid_point
Log score and time in 'cross_val_score'
check_scorable returns scorer
Clean up
Replace '_fit_estimator' by '_cross_val_score'
Fix PEP8, style and documentation
Remove wrong variable names
Remove helper function '_fit'
Remove 'fit_grid_point' from 'BaseSearchCV'
Check substrings of error messages
Rename '_split' to '_split_with_kernel'
_passthrough_scorer is a function
Remove '_deprecate_loss_and_score_funcs'
Check error message