v0.20 (2021-04-26)

• Added queue_name attribute to JobResult, #198
• set job_deserializer, job_serializer and default_queue_name on worker pools to better supported
  nested jobs, #203, #215 and #218
• All job results to be kept indefinitely, #205
• refactor cron jobs to prevent duplicate jobs, #200
• correctly handle CancelledError in python 3.8+, #213
• allow jobs to be aborted, #212
• depreciate pole_delay and use correct spelling poll_delay, #242
• docs improvements, #207 and #232