[SPARK-963] Wait for SparkListenerBus eventQueue to be empty before checking jobLogger state
Emit warning when task size > 100KB
Merge pull request #212 from markhamstra/SPARK-963

[SPARK-963] Fixed races in JobLoggerSuite
Merge pull request #207 from henrydavidge/master

Log a warning if a task's serialized size is very big

As per Reynold's instructions, we now create a warning level log entry if a task's serialized size is too big. "Too big" is currently defined as 100kb. This warning message is generated at most once for each stage.