Twitch.tv expandos

As suggested in [this reddit post.](https://www.reddit.com/r/Enhancement/comments/2krgic/feature_request_any_possibility_of_working/)
Tested in Chrome and Firefox on PC, could possibly use testing (if you think it's necessary) on Mac / other browsers (see [/r/speedrun](https://www.reddit.com/r/speedrun) for test links).

* Plays both streams and VOD (highlights)
* Conforms to autoplay settings
* Works with autoMaxHeight of comments and self-text