Normalize() transform has undocumented side effect

[keunhong]

It seems like F.normalize() does all of its operations in-place.

I feel like this should either be very clearly documented or be hidden behind a flag.

This really bit me when I was just sending some batch images to Visdom but my denormalization function was silently denormalizing my batch before doing a forward pass on the network. It was hidden to me until now and surfaces because a copy disappeared when I removed all Variable() wrappers.