title: Posting Json as Entity with scalaj-http
body: <p>the api of scalaj-http is clean and I would like to use it for a new project, but it usually post a Json in StringEntity as parameter, like this</p>
  
  <pre><code>        JSONObject TokenRequest = new JSONObject()
              .put("Credentials", new JSONObject()
                  .put("Username",  username)
                  .put("Password",  password));
  
          StringEntity requestBody = new StringEntity(TokenRequest.toString());
  
          httppost.setEntity(requestBody);
  </code></pre>
  
  <p>Not sure if it doable with scalaj-http?</p>