added test cases for sparse coding
added test cases for sparse coding

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