add 6.4.3 to CHANGELOG

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

CHANGELOG

@@ -9,6 +9,9 @@ v 6.5.0
   - Enable secure cookies if https used
   - Protect users/confirmation with rack_attack
 
+v6.4.3
+  - Don't use unicorn worker killer if PhusionPassenger is defined
+
 v6.4.2
   - Fixed wrong behaviour of script/upgrade.rb
 
@@ -605,4 +608,4 @@ v 0.8.0
   - stability
   - security fixes
   - increased test coverage
-  - email notification
\ No newline at end of file
+  - email notification