anchor.diff:  
   [source,js]
   --------------------------------------------------
  -$ curl -XPUT 'localhost:9200/_bench/?pretty=true' -d
  -'{
  +$ curl -XPUT 'localhost:9200/_bench/?pretty=true' -d '{
       "name": "my_benchmark",
       "competitors": [ {
           "name": "my_competitor",
  
positive.code:             "fields": ["title"]
          }
      } ]
  }
  --------------------------------------------------
  
  Response:
  
negative.code: 
  [source,js]
  --------------------------------------------------
  $ curl -XPUT 'localhost:9200/_bench/?pretty=true' -d '{
      "name": "my_benchmark",
      "num_executor_nodes": 1,
      "percentiles" : [ 25, 50, 75 ],
  