http://deeplearning.cs.cmu.edu/recitations/rec8.attention.pdf
https://github.com/cmudeeplearning11785/deep-learning-tutorials/blob/master/recitation-8/numbers_colors.ipynb
http://deeplearning.cs.cmu.edu/recitations/rec8.attention.pdf
https://github.com/cmudeeplearning11785/deep-learning-tutorials/blob/master/recitation-8/numbers_colors.ipynb