Document the new features

HISTORY.rst

@@ -1,10 +1,10 @@
 Changelog
 ---------
 
-- Adds the ability to depend on not a specific field value.
-  [msom]
+- Adds new options on how to dependen on a field value.
 
-- Adds the ability to depend on more then one fields (AND).
+  It's now possible to depend on NOT a specific field value and to depend on
+  more then one fields (AND).
   [msom]
 
 0.11.2 (2016-05-11)

onegov/form/core.py

@@ -362,6 +362,17 @@ def __call__(self, *args, **kwargs):
 class FieldDependency(object):
     """ Defines a dependency to a field. The given field(s) must have the given
     choice for this dependency to be fulfilled.
+
+    It's possible to depend on NOT the given value by preceeding it with a '!':
+
+        FieldDependency('field_1', '!choice_1')
+
+    To depend on more than one field, add the field_id's and choices to the
+    constructor:
+
+        FieldDependency('field_1', 'choice_1')
+        FieldDependency('field_1', 'choice_1', 'field_2', 'choice_2')
+
     """
 
     def __init__(self, *kwargs):