Not a real pull request, just to show what I've tried

This is just to show what I've tried. It is not meant to be pulled!

I've tried keeping refs to the NSPersistentStoreCoordinator, NSManagedObjectContext and NSPersistentStore in the App Delegate, just in case they were being prematurely deallocated. No dice.

I also tried the naïve approach of deferring the call to `self.completedCoreDataSetup`. Again, no dice.

I have at least narrowed it down to the line commented "// here's where the problem is"