The Enqueuer is responsible for enqueueing jobs into Redis.

It can either be called directly by the client, or instantiated as a standalone process.

It supports enqueuing immediate jobs, or scheduling jobs in the future.

Initialization:

• :name - Name of target registered process
• :namespace - Redis namespace to store all data under. Defaults to "exq".
• :queues - Array of currently active queues (TODO: Remove, I suspect it's not needed).
• :redis - pid of Redis process.
• :scheduler_poll_timeout - How often to poll Redis for scheduled / retry jobs.