Importing math/ranger

Ranger is a fast implementation of random forest (Breiman 2001) or
recursive partitioning, particularly suited for high dimensional
data. Classification, regression, probability estimation and survival
forests are supported. Classification and regression forests are
implemented as in the original Random Forest (Breiman 2001), survival
forests as in Random Survival Forests (Ishwaran et al. 2008). For
probability estimation forests see Malley et al. (2012).

(cheusov)