Adds CHANGELOG entry for #76

Author: weierophinney

CHANGELOG.md

@@ -2,15 +2,18 @@
 
 All notable changes to this project will be documented in this file, in reverse chronological order by release.
 
-## 3.1.0 - TBD
+## 3.1.0 - 2018-06-05
 
 ### Added
 
 - Nothing.
 
 ### Changed
 
-- Nothing.
+- [#76](https://github.com/zendframework/zend-expressive-router/pull/76) modifies the `RouteMiddlewareFactory` to allow specifying a string
+ `$routererviceName` to its constructor. This change allows having discrete
+ factory instances for generating route middleware that use different router
+ instances.
 
 ### Deprecated