DOC: Update changelog

CHANGELOG.md

@@ -11,10 +11,20 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - XMLTextNodeConverter for converting text nodes created by XMLTagConverter
 - XMLAttributeNodeConverter for converting attribute nodes created by XMLTagConverter
-- Units for properties.
+- Units for properties. They can be specified by giving the property as a dict in the form 
+  ```yaml
+  MyRecord:
+    my_prop:
+	  value: 5
+	  unit: m
+  ```
 
 ### Changed ###
 
+- Property values specified by dicts do not have to contain a
+  `collection_mode` key anymore. If none is given, the
+  `collection_mode` is determined from the `value`.
+
 ### Deprecated ###
 
 ### Removed ###