Add detailed documentation to OverSampler
Add detailed documentation to OverSampler

Make the ratio parameter be more understandable.
dvro/imbalanced-learn,scikit-learn-contrib/imbalanced-learn,glemaitre/UnbalancedDataset,glemaitre/UnbalancedDataset,dvro/UnbalancedDataset,fmfn/UnbalancedDataset,dvro/imbalanced-learn,dvro/UnbalancedDataset,fmfn/UnbalancedDataset,scikit-learn-contrib/imbalanced-learn