title: Extract response json string from akka http javadsl ResponseEntity
body: <p>I'm trying to make request to facebook REST APIs and in return getting a JSON Response. I'm able to collect the response in REST client, hence I know the requestUrl I'm using while creating HttpRequest in following code is correct. But when I try to mimick the GET using akka-http javadsl, I'm unable to understand how to extract the json from the ResponseEntity.</p>
  
  <pre><code>final HttpRequest request = HttpRequest.GET(requestUrl);
  final Materializer materializer = ActorMaterializer.create(this.context.getActorSystem());
  
  final CompletionStage&lt;HttpResponse&gt; responseFuture =
                  Http.get(this.context.getActorSystem()).singleRequest(request, materializer);
  
  final HttpResponse response = responseFuture.toCompletableFuture().get();
  </code></pre>
  
  <p>I'm expecting a response something as follows -</p>
  
  <pre><code> {
     "data": [
        {
           "cpc": 9.7938056680162,
           "clicks": "247",
           "impressions": "15949",
           "spend": 2419.07,
           "date_start": "2016-06-15",
           "date_stop": "2016-08-13"
        }
     ],
     "paging": {
        "cursors": {
           "before": "MAZDZD",
           "after": "MAZDZD"
        }
     }
  }
  </code></pre>