Update CHANGELOG

CHANGELOG.md

@@ -4,6 +4,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## 1.3.1 - 2018-06-19
+### Changed
+- Fixed bug with Federal District and missing cities in classroom count
+
 ## 1.3.0 - 2018-06-18
 ### Added
 - Daily charge amount route