Rock and Roll with Ember.js updated to Ember 2.2.0

I have updated the app developed in the Rock and Roll with Ember.js book to Ember 2.2 and Ember CLI 1.13.12. I also replaced the now defunct Divshot deployment section with another great & simple deployment option, PageFront.

Above that, there is a great deal of "bug fixes and stability improvements" in this release, the list of which can be viewed on Github.

Thank you to everybody who reported issues and helped to improve the book.