Features
* Add explicit exceptions
* Add task-request (activity and decision) no-tasks callback
Changes
* Make 'control' the last parameter for all relevant decisions
* Fix 'send_heartbeat' method name
* Move 'undeprecate_activity' 'domain' parameter to last positional
Fixes
* Add execution-start input parameter
* Fix activity/workflow deserialisation
* Fix polling invocations
* Fix task timed-out event deserialisation
Improvements
* Add attribute documentation for all but history
Miscellaneous
* Add link to docs in README and PyPI page