Merge branch 'dev' of github.com:mesos/spark into dev

core/src/main/scala/spark/SparkContext.scala

core/src/main/scala/spark/network/ConnectionManager.scala

core/src/main/scala/spark/scheduler/DAGScheduler.scala

core/src/main/scala/spark/scheduler/ShuffleMapTask.scala

core/src/main/scala/spark/storage/BlockManager.scala

core/src/main/scala/spark/storage/BlockManagerMaster.scala

core/src/main/scala/spark/storage/BlockManagerWorker.scala

core/src/main/scala/spark/storage/BlockStore.scala

core/src/main/scala/spark/storage/StorageLevel.scala

core/src/test/scala/spark/ShuffleSuite.scala

core/src/test/scala/spark/storage/BlockManagerSuite.scala

sbt/sbt