title: no suitable user-defined conversion from utility::string_t to std::string
body: <p>I am using the casablanca C++ Rest library to make HTTP requests.</p>
  
  <p>The problem is that this gives a utility::string_t string as output and I can't quite find any way to convert this to a classic std::string. Any ideas?</p>
  
  <pre><code>client.request(methods::GET).then([](http_response response)
  {
    if(response.status_code() == status_codes::OK)
    {
      string_t s = response.extract_string().get();
    }
  });
  </code></pre>