added comment

lib/weixin_authorize.rb

@@ -16,7 +16,7 @@ module WeixinAuthorize
 
     def http_post_without_token(url, payload={}, headers={}, endpoint="plain")
       post_api_url = endpoint_url(endpoint, url)
-      payload = MultiJson.dump(payload) if endpoint == "plain" # to json
+      payload = MultiJson.dump(payload) if endpoint == "plain" # to json if invoke "plain"
       load_json(RestClient.post(post_api_url, payload, headers))
     end