make setupAudioSession public and do not call it by default

VIMVideoPlayer-Source/VIMVideoPlayer.h

@@ -58,6 +58,10 @@ static const float TimeUpdateInterval = 0.1f;
 - (void)setPlayerItem:(AVPlayerItem *)playerItem;
 - (void)setAsset:(AVAsset *)asset;
 
+// AVAudioSession
+
+- (void)setupAudioSession;
+
 // Playback
 
 - (void)play;

VIMVideoPlayer-Source/VIMVideoPlayer.m

@@ -82,8 +82,6 @@ - (instancetype)init
         [self setupPlayer];
 
         [self addPlayerObservers];
-
-        [self setupAudioSession];
     }
 
     return self;