Difference Target Propagation
Independent reimplementation according to http://arxiv.org/abs/1412.7525
Using MNIST loading routines from https://github.com/oxford-cs-ml-2015/practical3
denoising_mnist.lua : BackProp training implementation for reference
denoising_mnist_targetprop.lua : TargetProp training implementation
To run use: th <script-name>