TODO

- Implement a housekeeping module that performs garbage collection in either the housekeeper binary or on the client.
  - clients should be able to run it in the background
- Track state for each task. Something like:
  enum TaskState {
    PENDING,    // task has been inserted into the queue
    CONSUMED,   // task has been consumed by the consumer
    RUNNING,    // consumer has indicated that progress has started on the task
    PROGRESS(%),// consumer can possibly report progress through the task?
    SUCCESS,    // task has completed
    FAILURE,    // task has failed
    LOST        // task has has been lost
  }
  state should be set to success on ZkMQMessage drop and maybe have a method to set state explicitly?

- consumer registration to the queue's members znode (/dir/consumers/<id>) and publish task information and stats
- consumer registration to the queue's members znode (/dir/producers/<id>) and publish stats?