update docs

CHANGES.md

@@ -4,8 +4,10 @@ CHANGES
 ## 3.1.3-RC
 
 * Feature: Write comment with Markdown
+* Improvement: Omit unnecessary response header
 * Fix: HTML escaped characters in markdown are unescaped unexpectedly after page is saved
 
+
 ## 3.1.2
 
 * Feature: Template page