zeppelin git commit: ZEPPELIN-3337. Add more test to SparkRInterpreter

Repository: zeppelin Updated Branches: refs/heads/branch-0.8 257db1d5a -> e91837cd5 ZEPPELIN-3337. Add more test to SparkRInterpreter ### What is this PR for? Add more test for SparkRInterpreter, and also some code refactoring in SparkRInterpreter. Also fix one bug of SparkRInterpreter that

zeppelin git commit: ZEPPELIN-3337. Add more test to SparkRInterpreter

Repository: zeppelin Updated Branches: refs/heads/master 5499fc4e9 -> e30fe73e9 ZEPPELIN-3337. Add more test to SparkRInterpreter ### What is this PR for? Add more test for SparkRInterpreter, and also some code refactoring in SparkRInterpreter. Also fix one bug of SparkRInterpreter that it c