Update the readme
Update the readme

Move the Common Problems to wiki page and reorder the Get Started section

dreampiggy/SDWebImage,Insfgg99x/SDWebImage,dreampiggy/SDWebImage,iheartradio/SDWebImage,awkward/SDWebImage,tualatrix/SDWebImage,dreampiggy/SDWebImage,zhang-yawei/SDWebImage,smule/SDWebImage,awkward/SDWebImage,awkward/SDWebImage,rs/SDWebImage