Added new train_folds parameter (#5114)
Added new train_folds parameter (#5114)

https://stackoverflow.com/questions/32433458/how-to-specify-train-and-test-indices-for-xgb-cv-in-r-package-xgboost/51412073
dmlc/xgboost,dmlc/xgboost,dmlc/xgboost,dmlc/xgboost,dmlc/xgboost,dmlc/xgboost