Added

• XCGLogger, and APIs for logging to a file and monitoring log file changes
• Dittojay demo app as a virtual Bluetooth LE heart rate sensor
  • Also allows testing background state restoration

Changed

• Migrate to Swift 4.2
• Dropped support for iOS 9
• Removed outdated or soon-to-be-replaced demo projects and documentation
• Redo, clean up, and improve Bluejay demo app to work with Dittojay demo.
• Restrict public access to Peripheral

Fixed

• Background and listen restoration callbacks
• Multiple listen crash by allowing trapping or replacing an existing listen
• Order of queueing when discovering services and characteristics
• Thread-related crashes by adding main thread safety checks to important Bluejay API calls