Add changelog for 3.4.1

CHANGELOG-3.4.md

@@ -12,8 +12,14 @@ where XXX and YYY are the older and newer versions, respectively.
 To generate a changelog summary since the last version, run
 `git log --no-merges --oneline XXX...HEAD`
 
-3.4.x-dev
----------
+3.4.1 (2017-11-18)
+------------------
+
+All issues and pull requests in this release may be found under the [3.4.1 milestone](https://github.com/doctrine/DoctrineMongoDBBundle/issues?q=milestone%3A3.4.1).
+
+ * [438](https://github.com/doctrine/DoctrineMongoDBBundle/pull/438) removes deprecated ODM functionality in tests
+ * [437](https://github.com/doctrine/DoctrineMongoDBBundle/pull/437) declares commands as services to make them discoverable with Symfony 4
+ * [433](https://github.com/doctrine/DoctrineMongoDBBundle/pull/433) fixes the container configuration to make services public for Symfony 4
 
 3.4.0 (2017-09-22)
 ------------------