torch7 implementation of the Ladder Network as explained in
Require following torch packages
nn
nngraph
optim
dp
dpnn
References
[1] Rasmus, Antti, Harri Valpola, and Tapani Raiko. "Lateral
Connections in Denoising Autoencoders Support Supervised Learning."
arXiv preprint arXiv:1504.08215 (2015).