Update CHANGELOG.md in preparation for release

Author: realityforge

CHANGELOG.md

@@ -1,6 +1,7 @@
 # Change Log
 
-### Unreleased
+### [v0.57](https://github.com/react4j/react4j-widget/tree/v0.57) (2018-03-28)
+[Full Changelog](https://github.com/react4j/react4j-widget/compare/v0.56...v0.57)
 
 Update the 'org.realityforge.react4j' dependencies to version '0.57'
 ### [v0.56](https://github.com/react4j/react4j-widget/tree/v0.56) (2018-03-28)