Refactor feedforward network test for new network API.
Refactor feedforward network test for new network API.

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