Fix typo in imagenet/main.py (pytorch#135)

Author: joaqo

imagenet/main.py

@@ -112,7 +112,7 @@ def main():
  batch_size=args.batch_size, shuffle=False,
  num_workers=args.workers, pin_memory=True)
 
- # define loss function (criterion) and pptimizer
+ # define loss function (criterion) and optimizer
  criterion = nn.CrossEntropyLoss().cuda()
 
  optimizer = torch.optim.SGD(model.parameters(), args.lr,