sketch of xgboost-spark

chooseBestBooster shall be in Boosters

remove tracker.py

rename XGBoost

remove cross-validation

jvm-packages/xgboost4j/src/test/java/ml/dmlc/xgboost4j/BoosterImplTest.java

@@ -130,6 +130,6 @@ public class BoosterImplTest {
     //do 5-fold cross validation
     int round = 2;
     int nfold = 5;
-    String[] evalHist = XGBoost.crossValiation(param, trainMat, round, nfold, null, null, null);
+    String[] evalHist = XGBoost.crossValidation(param, trainMat, round, nfold, null, null, null);
   }
 }

jvm-packages/xgboost4j/src/test/scala/ml/dmlc/xgboost4j/scala/ScalaBoosterImplSuite.scala

@@ -85,6 +85,6 @@ class ScalaBoosterImplSuite extends FunSuite {
       "objective" -> "binary:logistic", "gamma" -> "1.0", "eval_metric" -> "error").toMap
     val round = 2
     val nfold = 5
-    XGBoost.crossValiation(params, trainMat, round, nfold, null, null, null)
+    XGBoost.crossValidation(params, trainMat, round, nfold, null, null, null)
   }
 }