Remove terminal notifier from guard.
Run specs individually for easier figuring out of where a failure is.
Gates::Actor should use Actor.wrappable? for #protects?.

Reduces duplication.
Fix rspec duplicate shared examples error.
Miss adapter require for dsl spec.
Failing test for percentage of actors gate detection in Feature.
Use thing class instead of struct in actor spec.
Use actor class instead of repeating with struct in integration spec.
Multiline the if statement argument check in actor.
Dramatically simplify life by forcing flipper_id instead of id.

The big problem with just checking id is that EVERYTHING responds to id
even if it doesn't, due to the ruby deprecation warning for using
object_id instead of id.

#1. This change makes it super easy to detect actors because no one
will have a flipper_id method already in their models.

#2. This allows people to change what is used for activating individual
actors. If you don't want it to be id, simply define flipper_id to be
name, or whatever else you want.