Fix issue #2
I'm having a SIGABRT when using [SimpleAudioPlayer playFile:@"sound.wav"];

'NSInvalidArgumentException', reason: '-[AVAudioPlayer completionBlock]: unrecognized selector sent to instance 0x10ad2c150'

But it does work with WithCompletionBlock:
[SimpleAudioPlayer playFile:@"sound.wav" withCompletionBlock:^(BOOL finished) { }];