Added Pause Callback

[Duhduh1973]

Adds a callback for the pause function. Example usage: Pause a song without removing the "amplitude-active-song-container" class - allowing the active element to retain its styling while in pause mode.

Amplitude.config function:

"callbacks":
    "debug": true,
    "after_pause": "active_pause"
    }

});
function active_pause(){
    console.log('PAUSED');
    $('.amplitude-active-song-container').collapse('hide');
    $('.amplitude-active-song-container').prev().removeClass('active-panel');
    $('.amplitude-active-song-container').prev().find('.amplitude-play-pause').removeClass('amplitude-playing').addClass('amplitude-paused');
    $('.amplitude-active-song-container').prev().find('.playlist-play').removeClass('playlist-play').addClass('playlist-paused');
}

Functional Method in Amplitude.js

/*
Pauses the active song. If it's live, it disconnects the stream.
*/
function privatePause(){
privateRunCallback('before_pause');


if( config.active_metadata.live ){
    privateDisconnectStream();
}
config.active_song.pause();
privateRunCallback('after_pause');
}

[danpastori]

Thanks for the pull request. Sorry for not getting back sooner, its been a bit crazy around here. We released Amplitude 3.0, so now this has a merge conflict.

What I will do is take what you have and updated it to work in Amplitude 3.1 on the next release.

Thanks for your contribution!