Added zca-whitening functions.
Added whitening tests.
Added whitening to the unsup package.
Added test for zca_colour.
Updated zca_colour test
Added missing argument to zca_whiten.
Added missing argument to zca_whiten.
AddedMinor code clean-up.
Added pca-whitening and unit tests.
Merge pull request #8 from andreirusu/master

Added PCA/ZCA whitening methods.