stream.hls: Remember cookies set by variant playlist response.
stream.hls: Remember cookies set by variant playlist response.

Resolves #258.

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