This implemenation is based on: Friedman, J., Hastie, T. and Tibshirani, R. (2008) Regularization Paths for Generalized Linear Models via Coordinate Descent. http://www-stat.stanford.edu/~hastie/Papers/glmnet.pdf
@author Yasser Ganjisaffar (http://www.ics.uci.edu/~yganjisa/)