Temporary (?) fix for NMatrix#gesdd

This should fix #211.

It seems that the workspace_size parameter is causing NMatrix#gesdd to fail. In NMatrix::LAPACK::gesdd the default workspace_size parameter is 100000, but is only 1 on NMatrix#gesdd. 

Making it consistent appears to get it working, but I can't help but think 100000 is kind of arbitrary. Was there a special reason 100000 was made the default value? And if we had a matrix that requires something larger than that would this fail? 

Perhaps this needs to be revisited, but for now this patch should get it working at least.