Update train.py

[jss367]

I'm getting the following error when I run this:

Exception has occurred: RuntimeError
Expected object of scalar type Long but got scalar type Int for argument #2 'target' in call to _thnn_nll_loss_forward
  File "C:\Users\Julius\Documents\GitHub\BOSS\PT-BOSS\train.py", line 133, in train_one_epoch
    loss_x = criteria_x(logits_x, lbs_x)
  File "C:\Users\Julius\Documents\GitHub\BOSS\PT-BOSS\train.py", line 302, in train
    train_one_epoch(**train_args)
  File "C:\Users\Julius\Documents\GitHub\BOSS\PT-BOSS\train.py", line 316, in <module>
    train()

I think this is because some of the variables are Ints but they need to be Longs, so I've converted them.