Add changelog for 0.4.0

CHANGELOG

@@ -11,5 +11,10 @@
 * Use latest smtp settings
 
 [0.3.0]
-* New base image 
+* New base image
 * Update to upstream 2.1.0
+
+[0.4.0]
+* New base image
+* Update to upstream 3.0.0
+* Enable optional single sign-on