updated changelog to reflect version update for offline fix

Author: yankev

CHANGELOG.md

@@ -4,6 +4,10 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+## [1.9.13] - 2016-05-19
+### Fixed
+- Fixed issue in offline mode related to the inability to reload plotly.js on page refresh and extra init_notebook_mode calls.
+
 ## [1.9.12] - 2016-05-16
 ### Added
 SSL support for streaming.