[jvm-packages] add Spark and XGBoost tutorial (#1649)
[jvm-packages] add Spark and XGBoost tutorial (#1649)

* add back train method but mark as deprecated

* add Spark and XGBoost tutorial

* fix scalastyle error

dmlc/xgboost,dmlc/xgboost,dmlc/xgboost,dmlc/xgboost,dmlc/xgboost,dmlc/xgboost