AFNetworking/AFNetworking — pull request #1805 by kylef (2014-02-08 10:07:09+00:00)
Title: Refactor session task state observing

1) Let's do all the logic in one place, when we setup the delegate. This removes having 4 different addObserver's and 4 different removeObserver's.

2) Using selectors for keypaths so we have compile time checking that a `state` method exists.