v0.5.0

Changed:

• Breaking changes in the producer module, refactored to expose a better API:
  • Rather than send_to_event_bus(...), relying code should now call get_producer().send(...).
  • The sync kwarg is gone; to flush and sync messages before shutdown, call get_producer().prepare_for_shutdown() instead.
• Clarify that config module is for internal use only.
• Implementation changes: Only a single Producer is created, and is used for all signals.