Add attribution for PR 277 to changelog

Author: jas14

CHANGELOG.md

@@ -15,7 +15,7 @@
 ### Bug fixes
 
 - Fix ActiveRecord's `attributes_for_super_diff` and tree builders related to Active Records to handle models that do not have a primary key.
-  ([#282](https://github.com/splitwise/super_diff/pull/282))
+  [#282](https://github.com/splitwise/super_diff/pull/282) by [@atranson-electra](https://github.com/atranson-electra)
 
 ### Other changes