Merge pull request #92 from tgravescs/sparkYarnFixClasspath

Fix the Worker to use CoarseGrainedExecutorBackend and modify classpath ...

...to be explicit about inclusion of spark.jar and app.jar.  Be explicit so if there are any conflicts in packaging between spark.jar and app.jar we don't get random results due to the classpath having /*, which can including things in different order.

(cherry picked from commit b84193c5b86d60f36624ae29169cf62e489005af)
Signed-off-by: Reynold Xin <rxin@apache.org>