Updates Podfile dependencies
Updates Pods
Removes Pods from User Header Search Paths
Fixes code referencing to AFNetworkingErrorDomain

AFNetworking’s AFNetworkingErrorDomain constant has been split into two
new strings:

- AFURLRequestSerializationErrorDomain
- AFURLResponseSerializationErrorDomain
Fixes EditPostViewController

WPEditorViewControllerDelegate’s editPostViewDismissed has been deleted.

This commit updates EditPostViewController, so it doesn’t rely on that
delegate just to signal compeltion.
Reverts Podfile change
Merge remote-tracking branch 'origin/develop' into issue/1861-upgrades-afnetworking

Conflicts:
	Pods/Pods.xcodeproj/project.pbxproj
Merge pull request #1865 from wordpress-mobile/issue/1861-upgrades-afnetworking

Issue/1861 Upgrades AFNetworking
Merge branch 'develop' of github.com:wordpress-mobile/WordPress-iOS into issue/1868-cleanup-images

Conflicts:
	WordPress/WordPress.xcodeproj/project.pbxproj