voiceConnection.playing incorrectly returns true

In dev branch the VoiceConnection object returned from `client.joinVoiceChannel` will have `voiceConnection.playing` set to true even though nothing is currently playing. 

Issue is likely with [this](https://github.com/abalabahaha/eris/blob/dev/lib/core/VoiceConnection.js#L223) line.
