Rename MoleculeCSVDataset to MoleculeDataFrameDataset

[nbrosse]

MoleculeCSVDataset takes as input a pandas DataFrame. It would be more appropriate to rename it MoleculeDataFrameDataset

dgl-lifesci/python/dgllife/data/csv_dataset.py

Line 22 in a6f4596

class MoleculeCSVDataset(object):

[mufeili]

While I agree this name can be misleading, directly renaming it might break too much backward compatibility. One possible workaround is to add an alias of the class MoleculeDFDataset.

[nbrosse]

Yep, good idea !