plugins.ustreamtv: Add __repr__ to UHSStream.
plugins.ustreamtv: Add __repr__ to UHSStream.

Resolves #251.

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