Put changelog entry in Unreleased section

Author: stlehmann

CHANGELOG.md

@@ -2,9 +2,12 @@
 All notable changes to `dash` will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
-## [1.13.4] - 2020-06-25 
+## Unreleased
 ### Fixed
 - [#1315](https://github.com/plotly/dash/pull/1315) Add `update_title` parameter to set or disable the "Updating...." document title during updates. Closes [#856](https://github.com/plotly/dash/issues/856) and [#732](https://github.com/plotly/dash/issues/732)
+
+## [1.13.4] - 2020-06-25 
+### Fixed
 - [#1310](https://github.com/plotly/dash/pull/1310) Fix a regression since 1.13.0 preventing more than one loading state from being shown at a time.
 
 ## [1.13.3] - 2020-06-19