add filter to percent_missing
now only impute INPUT cols
add a save shortcut
improve doc
improve doc
fix double if on fillna
add filter to unique_values
improve comments
rewrite save
fix predict dtype
little improvents
move ensemble and estimators to core.estimators
rename PCAWrapper
move ensemble and estimators to core.estimators
improve bag and DivWrapper
rename DivWrapper to SplitWrapper
rewrite Bag.__init__