added changelog

Author: NullVoxPopuli

CHANGELOG.md

@@ -15,6 +15,7 @@ Fixes:
 Misc:
 
 - [#1984](https://github.com/rails-api/active_model_serializers/pull/1984) Make test attributes explicit. Test models have 'associations' support. (@bf4)
+- [#1993](https://github.com/rails-api/active_model_serializers/pull/1993) Swap out KeyTransform for CaseTransform gem for the possibility of native extension use (@NullVoxPopuli)
 
 ### [v0.10.3 (2016-11-21)](https://github.com/rails-api/active_model_serializers/compare/v0.10.2...v0.10.3)