Edit Code, Add RDKit and Mordred Descriptors

[HellenNamulinda]

This PR introduces several enhancements

Changes:

• Remove scaling of the descriptor features ( 9f89b58)
• Return features in a DataFrame instead of a Numpy array(1a9547b) to ensure the feature_names are used by shap.
• Initialize output folder at Regressor instantiation (264f581) where evaluation metrics and interpretability plots can be created. This is to remove redudant args in subsquent steps of evaluate and eplain.
• Add RDKit and Mordred descriptors (513f293).
• Compare the performance of feature selection using FeatureWiz (513f293)
• Update README.md