Add help message

@@ -29,12 +29,8 @@ var uts2time = new Date()
 
 var PushTimeId;
 console.log(TimeNow)
-var explain = 0;
 
 app.use(bodyParser.json());
-if(explain <1){
-    explain_message();
-}
 app.post('/hook', function (req, res) {
 
     var eventObj = req.body.events[0];
@@ -58,6 +54,10 @@ app.post('/hook', function (req, res) {
       PushTimeId = SetWhaleAlert()
       USER_ID = source.userId;
     }
+    else if(message.text == '도움말'){
+        explain_message();
+        USER_ID = source.userId;
+    }
     else if(message.text == '고래알람해제'){
       clearTimeout(PushTimeId)
     }