Added support for none active record model, which has no after_commit callabck.
This commit also includes the following changes -

  1. Refactored worker now
  2. Refactored async_callbacks now it's using ActiveSupport::Concern
  3. Added specs for after_destroy
Merge pull request #4 from we4tech/active_model_support

Added support for none active record model, which has no after_commit ca...