General cleanup

* remove unused Event::Mixins
* allow ignoring of subclasses of Model
* subclass Incident handlers and jobs
* fix guard bug where rspec wouldn't connect to spork
* add bullet to test env to get query log
* minor fixes
* dup the Rails.logger so we can change it without interfering
* switch rspec's new expect syntax
* slight refactor to subscription
* helper methods for classes that inherit from Revily::Model
* small cleanup
specs
update dependencies
remove validates_existence gem
pin active_model_serializers to exact git reference
add cane support
bump guard to v2
tiny cleanups