Minor cleanup.
Further simplify getOrElse call.
Refactor daemon thread pool creation.
Use default arguments instead of constructor overloads.
Merge pull request #400 from stephenh/sparkcontextcstrs

Use default arguments instead of constructor overloads.
Handle slaveLost before slaveIdToHost knows about it.
Merge pull request #402 from stephenh/handleslavelosttoosoon

Handle slaveLost before slaveIdToHost knows about it.
Merge pull request #399 from NFLabs/master

Fix for hanging spark.HttpFileServer on the kind of virtual network
Add an Avro dependency to REPL to make it compile with Hadoop 2
Merge pull request #404 from mbautin/master-fix-avro-dependency-in-repl

Add an Avro dependency to REPL to make it compile with Hadoop 2
Merge pull request #397 from JoshRosen/refactoring/daemon-threads

Refactor daemon thread creation
Merge remote-tracking branch 'stephenh/cleanup'

Conflicts:
	core/src/main/scala/spark/scheduler/local/LocalScheduler.scala
Add test for driver hanging on exit (SPARK-530).
Merge pull request #405 from JoshRosen/spark-530

Add test for driver hanging on exit (SPARK-530)