Updated CHANGELOG for #4

Author: weierophinney

CHANGELOG.md

@@ -6,7 +6,9 @@ All notable changes to this project will be documented in this file, in reverse
 
 ### Added
 
-- Nothing.
+- [#4](https://github.com/zendframework/zend-servicemanager/pull/4) updates the
+    `ServiceManager` to [implement the container-interop interface](https://github.com/container-interop/container-interop),
+    allowing interoperability with applications that consume that interface.
 
 ### Deprecated