New features:
1. Support iCloud Drive (for iOS 8 users)
2. Rotate element when editing fixed layout book or cover image
3. Cut, copy and paste elements from page to page
4. Support vertical text
5. Lock element to avoid movement
6. Add audio for each image of slideshow element
7. Show cover thumbnail when selecting book
8. Add justification option for alignment
9. Import multiple images to generate new book
10. Backup book to Dropbox automatically after generating book
11. Revamp Slideshow Element
12. Revamp Quiz Element
13. Optimized for iPhone 6 & iPhone 6 Plus
