README.md in fluent-plugin-elb-access-log-0.1.7 vs README.md in fluent-plugin-elb-access-log-0.1.8

@@ -41,9 +41,10 @@
   #tsfile_path /var/tmp/fluent-plugin-elb-access-log.ts
   #interval 300
   #start_datetime 2015/05/24 17:00
   #buffer_sec 600
   #history_length 100
+  #sampling_interval 1
   #debug false
 </source>
 ```
 
 ```javascript