rs/SDWebImage — pull request #139 by vesterbaek (2012-06-13 11:15:05+00:00)
Title: Fixed bugs when delegates add/cancel requests from delegate callbacks

Fixed bugs where callbacks via delegates or blocks could cause a crash since these might modify the downloaders, downloadInfo or downloadDelegates arrays if adding a new download request or canceling one from these.

This solution adds a small overhead, since arrays are iterated multiple times. I'm not sure if it is the best way to fix the bugs. Suggestions are welcome.