SPARK-1734: spark-submit throws an exception: Exception in thread "main"...

... java.lang.ClassNotFoundException: org.apache.spark.broadcast.TorrentBroadcastFactory

Author: witgo <witgo@qq.com>

Closes #665 from witgo/SPARK-1734 and squashes the following commits:

cacf238 [witgo] SPARK-1734: spark-submit throws an exception: Exception in thread "main" java.lang.ClassNotFoundException: org.apache.spark.broadcast.TorrentBroadcastFactory
(cherry picked from commit ec09acdd4a72333e1c9c2e9d8e12e9c4c07770c8)

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