Improve changelog layout

CHANGELOG.md

@@ -6,19 +6,24 @@ Changelog
 - AGPL license file
 
 ## 1.3.1 - 2018-12-14
-Fix: Some software instance types have different impact relations.
+### Fixed
+- Some software instance types have different impact relations.
 
 ## 1.3.0 - 2018-08-31
-Made module compatible with iTop 2.4+
+### Fixed
+- Made module compatible with iTop 2.4+
 
 ## 1.2.1 - 2016-08-30
-Added impact relations
+### Added
+- Impact relations
 
 ## 1.2.0 - 2016-08-26
-Added DB cluster
+### Added
+- DB cluster
 
 ## 1.1.0 - 2016-04-01
-Show software cluster list on software instances
+### Added
+- Show software cluster list on software instances
 
 ## 1.0.0 - 2016-03-30
 Initial release