Update release notes

Author: tomchristie

docs/topics/release-notes.md

@@ -42,6 +42,7 @@ You can determine your currently installed version using `pip freeze`:
 
 ### Master
 
+* Serializers now support bulk create and bulk update operations.
 * Regression fix: Date and time fields return date/time objects by default.  Fixes regressions caused by 2.2.2.  See [#743][743] for more details.
 * Bugfix: Fix 500 error is OAuth not attempted with OAuthAuthentication class installed.
 * `Serializer.save()` now supports arbitrary keyword args which are passed through to the object `.save()` method.  Mixins use `force_insert` and `force_update` where appropriate, resulting in one less database query.