Make separate validationLoss function in GradientTrainer optional
modify matrix_init
Fix minibatch implementation in DataManager
Add normalize transform; change matrix init
Add isRobust to Logistic layers
tune clipping procedure
Add z to feed_forward return and HiddenLayer backprop input
revamp HiddenLayer to handle new signature; implement robust logistic and tanh
move comment
Change Dy signature
compensate for change in Dy signature
compensate for change in Dy signature