Adding sinces

Author: davidkpiano

docs/api/Fieldset.md

@@ -34,6 +34,8 @@ const Address = () => (
 </Form>
 ```
 
+(since: 1.4.0)
+
 # Prop Types
 
 ## `model="..."` (required)

docs/guides/partial-models.md

@@ -71,3 +71,5 @@ With [`<Fieldset>`](../api/Fieldset), you can deeply resolve models:
 ```
 
 This makes it even easier to create reusable groups of controls.
+
+(since: 1.4.0)