Collaborative Filtering Package Improvements

by Sumedh Kedar Ghaisas for mlpack: scalable C++ machine learning library

'NMF, Non-Negative-Matrix factorization though fast and accurate, restricts the use of mean normalization due to its non-negativity constraint. This leads to the motivation of implementing SVD based matrix factorization methods which allows the addition of normalization and regularization. This project aims at building a strong CF module which will support most of the outperforming CF techniques as well as creating a solid backbone for future development by creating a robust abstraction.