rs/SDWebImage — pull request #942 by Krivoblotsky (2014-10-31 21:32:56+00:00)
Title: '304 Not Modified' HTTP status code handling.

Workaround for the issue:
https://github.com/rs/SDWebImage/issues/846#issuecomment-61299699
In case of 304 status code we need just cancel the request operation and return cached image from the cache.