CHANGELOG.md in lbfgsb-0.5.0 vs CHANGELOG.md in lbfgsb-0.5.1

@@ -1,4 +1,7 @@
+## 0.5.1
+- Refactor codes and configs with RuboCop.
+
 ## 0.5.0
 - Add build option to select FORTRAN integer bit size.
 
 ```
 $ gem install lbfgsb -- --with-use-int64