Multiple instance support and gapeless play

Support for multiple instances, each one streaming her own song to single/multiple devices.
-Filter each instance own hosts in udpServers by ip adress.
Note : fixed multiple host streaming the same song issue of first commit.

Gapeless play.
-Expose cirgularBuffer.reset() into Airtunes.reset() method
-Implement missing reportStatus method in airtune_device and coreAudio

When a device emit a "redy" event, call Airtunes.reset() and pipe the next song to airtunes.
```javascript
player.on('ready', function(){
// next song
  ffmpeg=spawn('ffmpeg_path', [arguments...,'pipe:1']);
  var bound = false;
  ffmpeg.on('data', function(){
   if (!bound){
    if (aitunes) airtunes.reset();
    ffmpeg.stdout.pipe(airtunes, { end: false });
   }
   bound = true;
  });
});
```
@Laurent
Thank you for your help to narrow down and fix this issue.