Add update message

Author: skuroda

messages.json

@@ -18,5 +18,6 @@
     "1.4.3": "messages/1.4.3.txt",
     "1.5.0": "messages/1.5.0.txt",
     "1.5.1": "messages/1.5.1.txt",
-    "1.6.0": "messages/1.6.0.txt"
+    "1.6.0": "messages/1.6.0.txt",
+    "1.7.0": "messages/1.7.0.txt"
 }