chore(*): release 0.2.1

[bungle]

Summary

• fix(tests): fix tests to not be order dependent on multi-worker scenario (fix(tests): fix tests to not be order dependent on multi-worker scenario #46)
• chore(callback): remove unnecessary assert when the type is already checked (chore(callback): remove unnecessary assert when the type is already checked #50)
• chore(queue): rename DEFAULT_QUEUE_LEN to more meaningful MAX_QUEUE_PREALLOCATE (chore(queue): rename DEFAULT_QUEUE_LEN to more meaningful MAX_QUEUE_PREALLOCATE #52)
• chore(callback): split get_callback_list to two functions to avoid unnecessary table creation (chore(callback): split get_callback_list to two functions to avoid unnecessary table creation #51)
• fix(worker): do not premature kill threads when not exiting (fix(worker): do not premature kill threads when not exiting #47)
• fix(broker): do not premature kill threads when not exiting (fix(broker): do not premature kill threads when not exiting #48)
• fix(worker): separate communication and event processing to different timers (fix(worker): separate communication and event processing to different timers #53) - caused by fix(worker): do not premature kill threads when not exiting #47