Lots of changes to enable much bigger images!
Lots of changes to enable much bigger images!

1. Use modal content and style loss modules similar to fast-neural-style
   for cleaner logic around network setup.
2. More memory-efficient Gram matrix implementation similar to
   fast-neural-style.
3. Multi-gpu support! Use nn.GPU decorators to compute different layers
   of the loss network on different GPUs.

ksemianov/neural-style,n1ckfg/neural-style,VaKonS/neural-style,shenyunhang/neural-style,jcjohnson/neural-style