title: c++ JsonCpp parse string with escaped quotes as array
body: <p>I've got the following json string:</p>
  
  <pre><code>{
      "data" : 
      [
          {
              "cart" : "[{\"name\":\"Test item 1\",\"price\":15,\"quantity\":1,\"sum\":15,\"tax\":\"none\",\"payment_type\":\"advance\",\"item_type\":\"service\"},{\"name\":\"Test item 2\",\"price\":13.01,\"quantity\":2,\"sum\":26.02,\"tax\":\"none\",\"payment_type\":\"part_prepay\",\"item_type\":\"work\"}]",
              "contact" : "noname@google.com",
              "p_id" : "603",
              "sum" : "100.02",
              "tax_system" : "osn"
          }
      ],
      "msg" : null,
      "result" : "success"
  }
  </code></pre>
  
  <p>I can parse <strong>cart</strong> as std::string after parsing input json string as stringstream:</p>
  
  <pre><code>const std::string ParseJsonData(std::stringstream ssJsonStream)
  {
      Json::Value jsonData;
      Json::Value responseData;
      Json::Value responseDataCart;
      Json::CharReaderBuilder jsonReader;
      std::string errs;
  
      if (Json::parseFromStream(jsonReader, ssJsonStream, &amp;jsonData, &amp;errs)) {
          responseData = jsonData["data"];
          responseDataCart = responseData[0]["cart"];
          return responseDataCart.toStyledString().c_str();
      }
      else
          return "Could not parse HTTP data as JSON";
  }
  </code></pre>
  
  <p>Please, tell me, how can i parse <strong>cart</strong> as array with JsonCpp?</p>