Enabled certificate pinning in demo project
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.
Add support for specifying a response serializer on a per-instance of `AFURLSessionManagerTaskDelegate`
[Issue #1833] Podspec fix.
[Issue #1772] Updates to 64 bit architecture

Signed-off-by: Mattt Thompson <m@mattt.me>
Merge pull request #1846 from lemonkey/master

[Issue #1833] Podspec fix.
Smaller clang diagnostic scope.
Merge pull request #1784 from jpsim/master

Enabled certificate pinning in demo project
Merge pull request #1723 from blakewatters/feature/allow-per-task-response-serializers

Add support for specifying a response serializer on `AFURLSessionManagerTaskDelegate`
Merge pull request #1805 from kylef/state-observing

Refactor session task state observing
Merge branch 'master' of github.com:AFNetworking/AFNetworking
Merge pull request #1847 from tewha/smaller-diagnostic-scope

Smaller clang diagnostic scope.
Update CHANGES for 2.1.0
Update CHANGES for 2.2.0
Bumping version to 2.2.0
Fix for -Wsign-conversion in AFURLConnectionOperation running Xcode 5.1
Resolves a -Wshorten-64-to-32 error on 32bit environments
Merge pull request #1856 from realestate-com-au/bug/xcode51-warnings

Fixes for a couple of errors with Xc5.1
Remove unnecessary #imports in UIImageView & UIWebView+AFNetworking headers.
Check CFStringTransform() call for success before using result