Use utf8 instead of ascii for string encoding.

Stumbled on this one when the node package [chromecast-js](https://github.com/guerrerocarlos/chromecast-js) was returning my chromecast devices with garbled letters where the utf-8 characters I used in their name should have been.

Dug all the way down through dependencies to find the source here. Is there a specific reason why ascii encoding is currently used or is this a valid change?