Update changelog

Author: mikebronner

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/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## [0.4.18] - 14 May 2019
+### Fixed
+- polymorphic relationship caching, as well as other queries using `InRaw`.
+
 ## [0.4.17] - 12 May 2019
 ### Fixed
 - generation of cache key where clauses.