Updated some comments for iOS 7+.
Removed a navigationBarStyle assignment.
Removed statusBarStyleSetting configuration. 

Replaced with alternative methods where required.
Setting translucency settings on the navigationBar.
Fixed section index visibility.
Removed document picker navigation bar transition. 

This caused flickering with the blurry background. The transition also doesn’t seem relevant for the current (iOS7+) navigation-bar styling.
Merge pull request #30 from PSPDFKit/matej/iOS8-and-iOS6-purge-fixes

[READY] iOS8 and iOS6 purge fixes.