Original site hosting mnist data (chpt4) gives 403

[djkramnik]

For chapter 4 the mnist data is giving a 403 (from mnist_download). This data is generally available on the internet though thankfully, i.e. here:

As of this writing, the necessary files are hosted here: https://github.com/golbin/TensorFlow-MNIST/blob/master/mnist/data/train-images-idx3-ubyte.gz

I know this repo is prob no longer maintained, but may be good to include the mnist.pkl, or at least the gzipped files that compromise it.