Add changelog for 3.1.0

CHANGELOG-3.1.md

@@ -0,0 +1,14 @@
+CHANGELOG for 3.1.x
+===================
+
+This changelog references the relevant changes (bug and security fixes) done in
+3.1 minor versions.
+
+3.1.0 (2018-12-21)
+------------------
+
+ - [270: Show the name of the database being purged when loading fixtures](https://github.com/doctrine/DoctrineFixturesBundle/pull/270) thanks to @alcaeus
+ - [265: Drop support for PHP < 7.1 and older versions of data-fixtures](https://github.com/doctrine/DoctrineFixturesBundle/pull/265) thanks to @alcaeus
+ - [260: Add fixture groups via a static method interface or service tags](https://github.com/doctrine/DoctrineFixturesBundle/pull/260) thanks to @weaverryan
+ - [269: Apply Doctrine Coding Standard](https://github.com/doctrine/DoctrineFixturesBundle/pull/269) thanks to @carusogabriel
+ - [219: Dynamic namespace](https://github.com/doctrine/DoctrineFixturesBundle/issues/219) thanks to @MassiveHiggsField