predict_proba returns a single matrix, so tuple unpacking fails

[ophiry]

in this line: https://github.com/TeamHG-Memex/eli5/blob/054e65688bd0bb738440da7f2f509d01afce0246/eli5/sklearn/utils.py#L49

there's an attempt to unpack the output of predict proba, but (at least in lightgbm) the return value is a matrix, so unpacking raises an exception not sure if this is also the case in other classifiers

ValueError: too many values to unpack (expected 1)