bugfix: make request time of leancloud saved and let concurrent requests pass (#519)

* bugfix: make request time of leancloud saved and let concurrency requests pass

* update code for a better style

* make code style consistent

* Update LEANCLOUD-COUNTER-SECURITY.md

Author: Maples7

docs/LEANCLOUD-COUNTER-SECURITY.md

@@ -64,10 +64,11 @@ Please note the difference between **site config file** and **theme config file*
   var query = new AV.Query("Counter");
   if (request.object.updatedKeys.indexOf('time') !== -1) {
       return query.get(request.object.id).then(function (obj) {
-          if (obj.get("time") + 1 !== request.object.get("time")) {
+          if (obj.get("time") > request.object.get("time")) {
               throw new AV.Cloud.Error('Invalid update!');
           }
-      })
+          return request.object.save();
+      });
   }
   ```
 

docs/zh-CN/LEANCLOUD-COUNTER-SECURITY.md

@@ -66,10 +66,11 @@ leancloud_visitors:
   var query = new AV.Query("Counter");
   if (request.object.updatedKeys.indexOf('time') !== -1) {
       return query.get(request.object.id).then(function (obj) {
-          if (obj.get("time") + 1 !== request.object.get("time")) {
+          if (obj.get("time") > request.object.get("time")) {
               throw new AV.Cloud.Error('Invalid update!');
-          }
-      })
+          } 
+          return request.object.save();
+      });
   }
   ```