use Luarocks prefix when installing "unsup"

use Luarocks prefix when installing "unsup"
Merge pull request #8 from andreirusu/master

Added PCA/ZCA whitening methods.
Merge pull request #5 from jhjin/patch-1

use Luarocks prefix when installing "unsup"
Refactored zca_layer to handle 2D, 3D & 4D inputs.
Refactored zca_colour and zca_layer tests to include 2D, 3D & 4D inputs.
Refactored test for zca_whitening to try 2D, 3D & 4D inputs.
Refactored pca_layer to support 2D, 3D & 4D inputs.
Refactored all pca whitening tests to check 2D, 3D & 4D inputs.
Added ZCA and PCA inverse tranform layers.
Added tests for inv_pca_layer and inv_pca_layer.
Updated inv_zca_layer_test to make sure it is equivalent to colouring.