Update CHANGELOG.md

Author: scls19fr

CHANGELOG.md

@@ -7,9 +7,13 @@ in every released version.
 
 ### Version 1.6.x
 - Released: 201x-xx-xx
+- Issues/Enhancements:
+  - Issue #99. Fix scatter plot direction
+
+### Version 1.6.4
+- Released: 2018-08-22
 - Issues/Enhancements:
   - Improve doc
-  - ...
 
 ### Version 1.6.3
 - Released: 2017-08-22