plugins.twitch: Update for API change.
plugins.twitch: Update for API change.

Resolves #633.

hmit/livestreamer,flijloku/livestreamer,streamlink/streamlink,programming086/livestreamer,jtsymon/livestreamer,fishscene/streamlink,wlerin/streamlink,Feverqwe/livestreamer,beardypig/streamlink,gtmanfred/livestreamer,chhe/streamlink,wolftankk/livestreamer,chhe/livestreamer,javiercantero/streamlink,intact/livestreamer,charmander/livestreamer,derrod/livestreamer,caorong/livestreamer,back-to/streamlink,chhe/livestreamer,melmorabity/streamlink,Klaudit/livestreamer,okaywit/livestreamer,programming086/livestreamer,gravyboat/streamlink,beardypig/streamlink,wolftankk/livestreamer,sbstp/streamlink,intact/livestreamer,mmetak/streamlink,wlerin/streamlink,Feverqwe/livestreamer,flijloku/livestreamer,ethanhlc/streamlink,chrippa/livestreamer,bastimeyer/streamlink,Masaz-/livestreamer,javiercantero/streamlink,okaywit/livestreamer,chhe/streamlink,Saturn/livestreamer,back-to/streamlink,bastimeyer/streamlink,derrod/livestreamer,Dobatymo/livestreamer,Masaz-/livestreamer,fishscene/streamlink,hmit/livestreamer,ethanhlc/streamlink,caorong/livestreamer,blxd/livestreamer,melmorabity/streamlink,mmetak/streamlink,chrippa/livestreamer,charmander/livestreamer,blxd/livestreamer,gtmanfred/livestreamer,jtsymon/livestreamer,lyhiving/livestreamer,streamlink/streamlink,Klaudit/livestreamer,sbstp/streamlink,gravyboat/streamlink,Dobatymo/livestreamer,lyhiving/livestreamer,Saturn/livestreamer