Add dependency on TransitionKit for state machines
Add state machine for easily implementing concurrent NSOperation subclasses
Add `performBlockAndWait:` invocation to RKFetchRequestManagedObjectCache
Drop parentOperation association and set concurrency limit to 1 on `connectionQueue` in `RKManagedObjectImporter`
Drop concurrency limit configuration from debugging
Implment dealloc to try and fight cxx_destruct crashes due to deallocation ordering