Merge branch 'release/2.0.0' into develop
Use non-translucent navigation bar instead of iOS 6/7 Deltas
Don't trim whitespaces and newlines twice
Make `initWithVideoIdentifier:` the designated initializer
Better error log when background playback would not work
Ensure that the video doesn't disappear after locking the device

Fixes #36

Techinal details: MPMoviePlayerViewController observes UIApplicationDidEnterBackgroundNotification through -[MPMoviePlayerViewController _moviePlayerViewController_applicationDidEnterBackgroundNotification:]. This method calls _shouldContinuePlaybackInBackground. If it returns NO (which it will do unless the app has the audio `UIBackgroundModes` Info.plist key) then [moviePlayer stop] is called which causes the movie player view controller to be dismissed (if presented with `presentMoviePlayerViewControllerAnimated:`) or the video view to be removed from its superview (if presented with `presentInView:`).
Do not crash when there is no current movie player controller

The app would crash when going to background very quickly after presenting a XCDYouTubeVideoPlayerViewController, i.e. `UIApplicationWillResignActiveNotification` is received before `MPMoviePlayerNowPlayingMovieDidChangeNotification`.
Interestingly, `objc_setAssociatedObject(nil, key, nil, …)` works fine but `objc_setAssociatedObject(nil, key, someNonNilObject, …)` crashes and this is exactly what happens when `currentMoviePlayerController` is still nil but we already have a `playerLayer` object.

Fixes #44
Rename notification selectors
Fix compilation issue with the iOS 8 SDK
Call `[super viewWillDisappear:animated]`
Fix crash on protected videos

The signature function name is `$n` so it fails the signature regular expression test. The XCDYouTubePlayerScript object is thus released early with a NULL context and JSGlobalContextRelease(NULL) crashes.

Fixes #46
Fix signature function regular expression
Improve thumnail parsing robustness
Update CHANGELOG
Update demo projects version to 2.0.1
Update version to 2.0.1
Merge branch 'release/2.0.1'