Refactor tests for changed NBC API.
Refactor tests for changed NBC API.

No new tests for Train() or empty constructor yet.

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