update CHANGELOG for 0.5.1 release
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9140573..7b6a638 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,8 @@
 ## 0.5.1
 
 * Experimental support for strong mode.
+* Fixed an issue with GeneratedMessage operator== and Map mixins
+* Added declaration of GeneratedMessage clone method
 
 ## 0.5.0+1