Fix SerializationSuite failures due to uninitialized SharkEnv and SharkContext.
Conflicts:

	src/main/scala/shark/SharkEnv.scala
	src/main/scala/shark/execution/serialization/KryoSerializer.scala
Always launch shark-shell with Java
Merge pull request #234 from harveyfeng/serialization

Fix SerializationSuite failures due to SharkContext NPE