Add NSObject Conformance to IGListUpdatingDelegate

Summary:
- [x] All tests pass. Demo project builds and runs.
- [x] I added tests, an experiment, or detailed why my change isn't tested.
- [x] I added an entry to the `CHANGELOG.md` for any breaking changes, enhancements, or bug fixes.
- [x] I have reviewed the [contributing guide](https://github.com/Instagram/IGListKit/blob/master/.github/CONTRIBUTING.md)
Closes https://github.com/Instagram/IGListKit/pull/435

Differential Revision: D4479614

Pulled By: rnystrom

fbshipit-source-id: cd0e734d01a53430ec0566f27bd9f39f3d17802c

CHANGELOG.md

@@ -20,6 +20,8 @@ This release closes the [3.0.0 milestone](https://github.com/Instagram/IGListKit
                         withObject:(id)object;
 ```
 
+- `IGListUpdatingDelegate` now conforms to `NSObject`, bringing it in line with other framework protocols. [Adlai Holler](https://github.com/Adlai-Holler) [(#435)](https://github.com/Instagram/IGListKit/pull/435)
+
 2.2.0
 -----
 

Source/IGListUpdatingDelegate.h

@@ -37,7 +37,7 @@ typedef void (^IGListReloadUpdateBlock)();
  Implement this protocol in order to handle both section and row based update events. Implementation should forward or
  coalesce these events to a backing store or collection.
  */
-@protocol IGListUpdatingDelegate
+@protocol IGListUpdatingDelegate <NSObject>
 
 /**
  Asks the delegate for the pointer functions for looking up an object in a collection.