Queueing system

QueueWorker uses luigi.interface to turn list of command line args
into Task.

QueueScheduler is abstract class for creating queue workers. Added
example implementation using HDFS as a queuing system.

Queues queues queues
Forgot an import
QueueWorker uses run instead of requires
Split up queueing and task deserialization
Fixes on_failure method call

Wasn't passing exception argument