Add serialization test.
Add serialization test.

ajjl/mlpack,darcyliu/mlpack,ajjl/mlpack,darcyliu/mlpack,theranger/mlpack,theranger/mlpack,ranjan1990/mlpack,ajjl/mlpack,palashahuja/mlpack,theranger/mlpack,ranjan1990/mlpack,darcyliu/mlpack,palashahuja/mlpack,palashahuja/mlpack,ranjan1990/mlpack