title: AVAudioPlayer pausing issue
body: <p>In my project, I have an AVAudioPlayer which plays a song. After I pause it, and hit   play again, it starts over instead of playing where I paused. Why is that happening?
  Also, when I press play for the first time, it loads the song about 3-4 seconds. I thought I solved it by loading it on the other thread, but it still loads too slow (at least the view doesn't freeze anymore). How can I fix that? Here's the code:</p>
  
  <pre><code>- (IBAction)play:(id)sender {
    songIsCurrentlyPaused = NO;
    if(songIsCurrentlyPaused==YES){
      [self.background play];
    } else {
      playQueue = dispatch_queue_create("volume_change", NULL);
      dispatch_async(playQueue, ^{ NSString *filePath = 
        [[NSBundle mainBundle]pathForResource:@"some_song" ofType:@"mp3"];
        NSURL *fileURL = [[NSURL alloc] initFileURLWithPath:filePath];
        self.background = [[AVAudioPlayer alloc] initWithContentsOfURL:fileURL error:nil];
        self.background.delegate = self;
        [self.background setNumberOfLoops:1];
        [self.background setVolume:0.5];
        [self.background play]; });
  
        [trackNameLabel setText:@"Currently playing :\n some_song"];
        self.timer = [NSTimer scheduledTimerWithTimeInterval:0.25 target:self selector:@selector(updateProgressBar) userInfo:nil repeats:YES];
      }
  }
  
  - (IBAction)pause:(id)sender {
    songIsCurrentlyPaused = YES;
    [self.background pause];
    [trackNameLabel setText:@"Currently playing : some_song (paused)"];
    [self.progressBar setProgress:self.background.currentTime/self.background.duration animated:YES];
  }
  </code></pre>
  
  <p>Thanks!</p>