code: protected <T> T doGet(String path, Class<T> cls) throws ClientException {
          return doGet(path, cls, null);
      }
docs: Gets the resource specified by the path. Sends to the server an Accepts
  header for JSON.
  
  @param <T> the type of the resource.
  @param path the path to the resource. Cannot be <code>null</code>.
  @param cls the type of the resource. Cannot be <code>null</code>.
  
  @return the resource.
  
  @throws ClientException if a status code other than 200 (OK) is returned.