A PyTorch implementation of the paper "Visualizing and understanding convolutional networks" and rely on https://github.com/csgwon/pytorch-deconvnet

1. add ReLU layers to deconvolutional network
2. delete "deconv_first_layers"
3. use hooks to get intermediate feature maps
4. add heatmap
5. other modifications to make the code more elegant

@inproceedings{zeiler2014visualizing,
  title={Visualizing and understanding convolutional networks},
  author={Zeiler, Matthew D and Fergus, Rob},
  booktitle={European conference on computer vision},
  pages={818--833},
  year={2014},
  organization={Springer}
}