Update README.
Update README.

New installer for Windows is now available.
fishscene/streamlink,wolftankk/livestreamer,melmorabity/streamlink,intact/livestreamer,wolftankk/livestreamer,bastimeyer/streamlink,flijloku/livestreamer,chhe/livestreamer,charmander/livestreamer,melmorabity/streamlink,bastimeyer/streamlink,mmetak/streamlink,okaywit/livestreamer,Feverqwe/livestreamer,intact/livestreamer,asermax/livestreamer,Masaz-/livestreamer,gtmanfred/livestreamer,okaywit/livestreamer,caorong/livestreamer,blxd/livestreamer,programming086/livestreamer,Feverqwe/livestreamer,jtsymon/livestreamer,derrod/livestreamer,back-to/streamlink,flijloku/livestreamer,Saturn/livestreamer,gravyboat/streamlink,chrisnicholls/livestreamer,ethanhlc/streamlink,wlerin/streamlink,hmit/livestreamer,chhe/livestreamer,Saturn/livestreamer,derrod/livestreamer,javiercantero/streamlink,breunigs/livestreamer,beardypig/streamlink,chhe/streamlink,chrippa/livestreamer,mmetak/streamlink,sbstp/streamlink,Klaudit/livestreamer,sbstp/streamlink,programming086/livestreamer,fishscene/streamlink,hmit/livestreamer,caorong/livestreamer,gtmanfred/livestreamer,breunigs/livestreamer,chhe/streamlink,Klaudit/livestreamer,javiercantero/streamlink,lyhiving/livestreamer,streamlink/streamlink,lyhiving/livestreamer,gravyboat/streamlink,back-to/streamlink,ethanhlc/streamlink,chrippa/livestreamer,beardypig/streamlink,Dobatymo/livestreamer,streamlink/streamlink,Masaz-/livestreamer,wlerin/streamlink,Dobatymo/livestreamer,charmander/livestreamer,jtsymon/livestreamer,blxd/livestreamer