anchor.diff:  GET /_search
   {
       "query" : {
  -        "match_all": {}
  +        "match": { "user": "kimchy" }
       },
       "highlight" : {
           "tags_schema" : "styled",
  
positive.code: GET /_search
  {
      "query" : {
          "match_all": {}
      },
      "highlight" : {
          "fields" : {
  
negative.code:     }
  }
  --------------------------------------------------
  
  ==== Force highlighter type
  
  The `type` field allows to force a specific highlighter type. This is useful
  