Initial revision.
Converted to Objective-C ARC using Xcode refactor tools.
Converted to Modern Objective-C syntax using Xcode refactor tools.
Added `SK` prefix to entities and provided info about dev environment and initial considerations.
Removed no longer needed declaration of ivars and @synthesize and @dynamic directives.
Integrated Cocoa Pods for test harness.
Updated code style using clang format tool.
Reworked dealing with Core Data repository: isolated CoreData-specific logic in repository and model objects.