Update Changelog for release of version 5.0.3

Author: LaunchDarklyCI

CHANGELOG.md

@@ -2,6 +2,12 @@
 
 All notable changes to the LaunchDarkly Python SDK will be documented in this file. This project adheres to [Semantic Versioning](http://semver.org).
 
+## [5.0.3] - 2018-04-10
+### Fixed
+- Fixed a bug that, in Python 3.x, caused an error when using an integer user attribute to compute a rollout.
+- Fixed a bug that, in Python 3.x, made the `all_flags` method return a dictionary with byte-string keys instead of string keys when using the Redis feature store.
+
+
 ## [5.0.2] - 2018-03-27
 ### Fixed
 - In the Redis feature store, fixed a synchronization problem that could cause a feature flag update to be missed if several of them happened in rapid succession.