title: Return top search results with unique title in Elasticsearch
body: <p>I have search results produced by Elasticsearch as follows:</p>
  
  <p>query: apple pie</p>
  
  <pre><code>1. title: apple pie, score: 144.67503
  2. title: apple pie, score: 128.19138
  3. title: apple, score: 59.768208
  4. title: apple, score: 39.49909
  5. title: red apple, score: 34.314064
  6. title: apple red, score: 34.014064
  </code></pre>
  
  <p>I want to have the following:</p>
  
  <pre><code>1. title: apple pie, score: 144.67503
  2. title: apple, score: 59.768208
  3. title: red apple, score: 34.314064
  4. title: apple red, score: 34.014064
  </code></pre>
  
  <p>How can I do that in Elasticsearch? It would be great if get the response in DSL.</p>