Minor Bugs caused by old version

[planemanner]

This issue is for pytorch 1.7+ version user

Line 148, 160 in main.py script

Line 148

100. * batch_idx / len(train_loader), loss.data[0]))

Line 160

test_loss += F.cross_entropy(output, target, size_average=False).data[0]

The end of those code lines should be revised as following
.data[0] -> .item()

I know most of guys using this repo can fix easily, but someone would be confused.
So I leave above minor tip in this issue.