Allow adding callbacks against multiple to states, and bump rubocop
Move multiple to states logic to Callback
README additions including FAQs and docs on testing
Tweaks to FactoryGirl stuff
Merge pull request #83 from gocardless/after-to-multiple

Allow adding callbacks against multiple to states, and bump rubocop
Merge pull request #88 from gocardless/readme

README Additions (FAQs and Testing)
Make ActiveRecordModel.in_state and ActiveRecordModel.not_in_state work with initial states
Enforce definition of self.initial_state, rather than self.state_machine_class on models
Added README, CHANGELOG
Alias first transition, so that the transitions table can still be joined on elsewhere