Allow spark on yarn to be run from HDFS. Allows the spark.jar, app.jar, and log4j.properties to be put into hdfs.
Add mockito to the sbt build
Merge pull request #137 from tgravescs/sparkYarnJarsHdfsRebase

Allow spark on yarn to be run from HDFS.

Allows the spark.jar, app.jar, and log4j.properties to be put into hdfs.  Allows you to specify the files on a different hdfs cluster and it will copy them over. It makes sure permissions are correct and makes sure to put things into public distributed cache so they can be reused amongst users if their permissions are appropriate.  Also add a bit of error handling for missing arguments.