Added CHANGELOG for #51

Author: weierophinney

CHANGELOG.md

@@ -18,7 +18,9 @@ All notable changes to this project will be documented in this file, in reverse
 
 ### Fixed
 
-- Nothing.
+- [#51](https://github.com/zendframework/zend-session/pull/51) provides a fix to
+  the `DbTableGateway` save handler to prevent infinite recursion when
+  attempting to destroy an expired record during initial read operations.
 
 ## 2.7.2 - 2016-06-24