Add test for DiagonalConstraint.
Add test for DiagonalConstraint.


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