Added CHANGELOG for #273

Author: weierophinney

CHANGELOG.md

@@ -23,6 +23,11 @@ Initial stable release.
 - [#268](https://github.com/zendframework/zend-expressive/pull/268) fixes the
   Pimple example within the `ServerUrlHelper` chapter of the documentation to
   use the Pimple v3 API instead of the v1 API.
+- [#273](https://github.com/zendframework/zend-expressive/pull/273) fixes the
+  verbiage used in the `ServerUrlHelper` documentation regarding when to
+  register the `ServerUrlMiddleware`; though the examples were correct, the
+  verbiage was indicating the middleware should be piped following routing,
+  rather than before.
 
 ## 1.0.0rc6 - 2016-01-18