code: function _request( options ) {
      options.headers = options.headers || {};
      options.headers[ 'X-OpenRosa-Version' ] = '1.0';
  
      const method = options.method || 'get';
  
      return new Promise( ( resolve, reject ) => {
          request[ method ]( options, ( error, response, body ) => {
              if ( error ) {
                  console.log( `Error occurred when requesting ${options.url}`, error );
                  reject( error );
              } else if ( response.statusCode === 401 ) {
                  const error = new Error( 'Forbidden. Authorization Required.' );
                  error.status = response.statusCode;
                  reject( error );
              } else if ( response.statusCode < 200 || response.statusCode >= 300 ) {
                  const error = new Error( `Request to ${options.url} failed.` );
                  error.status = response.statusCode;
                  reject( error );
              } else {
                  console.log( `response of request to ${options.url} has status code: `, response.statusCode );
                  resolve( body );
              }
          } );
      } );
  }
docs: Sends a request to an OpenRosa server. Only for basic retrieval of
  public forms that do not require authentication.
  
  @param  { {url: string, method: string} } options  request options object
  @return { Promise }