Bump version to 0.3.1

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Refactoring & add ability to filter hooks to fire based on instance

Add ability to cancel webhooks

Update CI

Update django-settings-holder version

Changes to serialization and client kwargs

- Change the signature of TASK_HANDLER to take **kwargs instead of kwargs.
- Hook model instance is serialized before TASK_HANDLER is called,
  meaning that delete hook will also have access to the instance id.
  The SERIALIZER setting no longer takes the "hook" argument.
- CLIENT_KWARGS can no longer be defined on the model. The CLIENT_KWARGS
  setting is now a global definition, which will be updated with the
  hook headers and serialized instance json. CLIENT_KWARGS also no longer
  takes the "instance" argument.
- Fix typo "thead_task_handler" to "thread_task_handler"

Update dependencies