Replaced a "note" by a "tip"

javiereguiluz · web-flow · commit e4eae257d14b · 2018-09-11T10:12:38.000+02:00
diff --git a/serializer.rst b/serializer.rst
@@ -133,7 +133,7 @@ to your class and choose which groups to use when serializing::
         'json', array('groups' => 'group1')
     );
 
-.. note::
+.. tip::
 
     The value of the ``groups`` key can be a single string, or an array of strings.
 
