Add draft convnet tutorial for BigMax workshop.

conv-nn-bigmax-2019/avg_pooling_example.png

conv-nn-bigmax-2019/bigmax_mnist_example_tutorial.ipynb

conv-nn-bigmax-2019/convolution_same_padding_no_strides.gif

conv-nn-bigmax-2019/img_berlin_landscape.jpg

conv-nn-bigmax-2019/img_max_planck.jpg

conv-nn-bigmax-2019/maxpool.jpg

conv-nn-bigmax-2019/mnist_examples.png

conv-nn-bigmax-2019/output_discrete_convolution.png

conv-nn-bigmax-2019/padding_strides.gif