Bug fix for pad_batch in models.py; Remove gradient fcns
Bug fix for pad_batch in models.py; Remove gradient fcns

ktaneishi/deepchem,Agent007/deepchem,miaecle/deepchem,peastman/deepchem,peastman/deepchem,deepchem/deepchem,lilleswing/deepchem,deepchem/deepchem,rbharath/deepchem,joegomes/deepchem,lilleswing/deepchem,joegomes/deepchem,ktaneishi/deepchem,miaecle/deepchem,lilleswing/deepchem,Agent007/deepchem,miaecle/deepchem,rbharath/deepchem,ktaneishi/deepchem,Agent007/deepchem