Fix link AFNetworking logo
Change download link

The download link in Readme should be to the 2.0 branch.
Pass returned disposition instead of forcing NSURLSessionAuthChallengePerformDefaultHandling
Fix broken UIButton KVC code
Merge pull request #1253 from a2/2.0

Fix broken UIButton KVC code
Merge pull request #1252 from getaaron/2.0

Pass disposition instead of forcing NSURLSessionAuthChallengePerformDefaultHandling
Merge pull request #1251 from xHunter/2.0

[2.0] Wrong links in Readme