justin: refactoring
justin: refactoring

Break out logic for video and channel fetching to functions and introduce a
JustinUrlException class, that represents faulty URLs.

selepo/svtplay-dl,leakim/svtplay-dl,spaam/svtplay-dl,olof/svtplay-dl,qnorsten/svtplay-dl,leakim/svtplay-dl,spaam/svtplay-dl,OakNinja/svtplay-dl,OakNinja/svtplay-dl,dalgr/svtplay-dl,OakNinja/svtplay-dl,qnorsten/svtplay-dl,olof/svtplay-dl,selepo/svtplay-dl,iwconfig/svtplay-dl,leakim/svtplay-dl,iwconfig/svtplay-dl,dalgr/svtplay-dl