Update CHANGELOG

CHANGELOG

+N/A [23.05.2016]
+    NOTE: The Namespace of EasyMySQLi in our GitLab changed from open-source-php to open-source.
+          Please update your upstream repo addresses if you cloned this repo.
+
 0.3b [09.05.2016]
     * Fixed an error when a parameter is NULL (previously it was treated as empty string, now it's a real NULL)
     * Added an error message when one tries to "querySinglerows/queryAllRows" on a statement not returning results like DELETE