rs/SDWebImage — pull request #588 by erikcharlebois (2013-12-16 19:54:09+00:00)
Title: Assign thread for downloada cancellation + minor doc fix

Fix a param mismatch causing a warning in our build.

Set the current thread when beginning an NSURLConnection so that cancellation can be put on their right thread (sorry about the first patch, that line was somehow removed in the merge).