updating change log and optimizing png

CHANGELOG.md

@@ -1,6 +1,7 @@
 # PrivateBin version history
 
   * **1.4 (not yet released)**
+    * ADDED: Option to send a mail with the link, when creating a paste (#398)
     * FIXED: Password disabling option (#527)
   * **1.3.1 (2019-09-22)**
     * ADDED: Translation for Bulgarian (#455)