Added a dedicated example screen for MRBlurView
Refactored setting of backgroundColor as placeholder
Set placeholder on initialization
Listen for UIApplicationDidChangeStatusBarOrientationNotification
instead of UIDeviceOrientationDidChangeNotification
Wait for the frame change, which will occur, until redraw is called
We must redraw async to fix the flicker issue

See #42.
Ensure to initially draw a blurred image
Merge pull request #45 from mrackwitz/fix/42_orientation_flicker

Fix #42: Flickering while orientation change