Neural style transfer as a class in PyTorch

Based on: https://github.com/alexis-jacq/Pytorch-Tutorials

Adds:

StyleTransferNet as a class that can be imported by other scripts

VGG support (this was before pretrained VGG models were available in PyTorch)

Convenience functions for saving intermediate style & content targets for display

Convenience function for examining gram matricies as images

Auto style, content, and product image saving

matplotlib plots of losses over time & record of hyperparameters to keep track of favorable results