Update Changelog for release of version 5.3.0

Author: LaunchDarklyCI

CHANGELOG.md

@@ -2,6 +2,13 @@
 
 All notable changes to the LaunchDarkly Ruby SDK will be documented in this file. This project adheres to [Semantic Versioning](http://semver.org).
 
+## [5.3.0] - 2018-10-24
+### Added:
+- The `all_flags_state` method now accepts a new option, `details_only_for_tracked_flags`, which reduces the size of the JSON representation of the flag state by omitting some metadata. Specifically, it omits any data that is normally used for generating detailed evaluation events if a flag does not have event tracking or debugging turned on.
+
+### Fixed:
+- JSON data from `all_flags_state` is now slightly smaller even if you do not use the new option described above, because it omits the flag property for event tracking unless that property is true.
+
 ## [5.2.0] - 2018-08-29
 ### Added:
 - The new `LDClient` method `variation_detail` allows you to evaluate a feature flag (using the same parameters as you would for `variation`) and receive more information about how the value was calculated. This information is returned in an `EvaluationDetail` object, which contains both the result value and a "reason" object which will tell you, for instance, if the user was individually targeted for the flag or was matched by one of the flag's rules, or if the flag returned the default value due to an error.