Refactor the cancel logic
Merge branch 'master' into new_cancel_logic

Conflicts:
	SDWebImage/MKAnnotationView+WebCache.m
	SDWebImage/UIButton+WebCache.m
	SDWebImage/UIImageView+HighlightedWebCache.h
	SDWebImage/UIImageView+HighlightedWebCache.m
	SDWebImage/UIImageView+WebCache.m
Merge pull request #771 from Whirlwind/new_cancel_logic

Refactor the cancel logic