add a startLoopBlock, A block to be called when in loop playback the loop restarts/begins again
Remove setting the playhead in startLoop Block

Remove setting the playhead in the main-thread notification method, cause it doubles with Line 160 and may create a jitter & click on loop boundary.
Merge pull request #55 from ploenne/master

Add a startLoopBlock on Class AEAudioFilePlayer
Minor tweaks to prior commit
Merge remote-tracking branch 'official/master'