Add some warnings, and make some minor fixes.
Add some warnings, and make some minor fixes.

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