[scikit-learn] Latent Semantic Analysis (LSA) and TrucatedSVD

[Olivier Grisel]

I am not sure this is exactly the same because we do not center the
data in the TruncatedSVD case (as opposed to the real PCA case where
whitening is the same as calling StandardScaler).

Having an option to normalize the transformed data by sigma seems like
a good idea but we should probably not call that whitening.

-- 
Olivier