Add function to get the current gradient.
Add function to get the current gradient.

ranjan1990/mlpack,stereomatchingkiss/mlpack,BookChan/mlpack,palashahuja/mlpack,thirdwing/mlpack,chenmoshushi/mlpack,theranger/mlpack,theranger/mlpack,BookChan/mlpack,erubboli/mlpack,ajjl/mlpack,darcyliu/mlpack,bmswgnp/mlpack,chenmoshushi/mlpack,thirdwing/mlpack,lezorich/mlpack,ajjl/mlpack,ajjl/mlpack,erubboli/mlpack,darcyliu/mlpack,palashahuja/mlpack,trungda/mlpack,palashahuja/mlpack,darcyliu/mlpack,bmswgnp/mlpack,stereomatchingkiss/mlpack,ersanliqiao/mlpack,stereomatchingkiss/mlpack,trungda/mlpack,BookChan/mlpack,lezorich/mlpack,bmswgnp/mlpack,erubboli/mlpack,trungda/mlpack,ersanliqiao/mlpack,theranger/mlpack,ranjan1990/mlpack,ersanliqiao/mlpack,thirdwing/mlpack,ranjan1990/mlpack,chenmoshushi/mlpack,lezorich/mlpack