Remove unused cudnn dependency.

docs/setup.md

@@ -141,7 +141,6 @@ where `$NAME` is as listed below.
 + [nn](https://github.com/torch/nn)
 + [optim](https://github.com/torch/optim)
 + [csvigo](https://github.com/clementfarabet/lua---csv)
-+ [cudnn.torch](https://github.com/soumith/cudnn.torch) (only for CUDA support)
 + [fblualib](https://github.com/facebook/fblualib)
   (only for [training a DNN](http://cmusatyalab.github.io/openface/training-new-models/))
 

training/model.lua

@@ -1,6 +1,5 @@
 require 'nn'
 require 'cunn'
-require 'cudnn'
 require 'dpnn'
 
 require 'optim'