https://arxiv.org/abs/1508.04025
https://github.com/ywk991112/pytorch-chatbot
https://github.com/spro/practical-pytorch/tree/master/seq2seq-translation
https://github.com/floydhub/textutil-preprocess-cornell-movie-corpus
https://www.cs.cornell.edu/~cristian/Cornell_Movie-Dialogs_Corpus.html
https://pytorch.org/tutorials/beginner/chatbot_tutorial.html