delete no use var

Author: wangfei <wangfei_hello@126.com>

Closes #613 from scwf/masterIndex and squashes the following commits:

1463056 [wangfei] delete no use var: masterIndex
(cherry picked from commit 4bf24f7897e1c67ca5f96dec05480e571f05ee1d)

Signed-off-by: Patrick Wendell <pwendell@gmail.com>
SPARK-1492. Update Spark YARN docs to use spark-submit

Author: Sandy Ryza <sandy@cloudera.com>

Closes #601 from sryza/sandy-spark-1492 and squashes the following commits:

5df1634 [Sandy Ryza] Address additional comments from Patrick.
be46d1f [Sandy Ryza] Address feedback from Marcelo and Patrick
867a3ea [Sandy Ryza] SPARK-1492. Update Spark YARN docs to use spark-submit
(cherry picked from commit 2b961d88079d7a3f9da63d5175d7b61f6dec762b)

Signed-off-by: Patrick Wendell <pwendell@gmail.com>