code: function(imageIdentifier, options) {
          if (typeof imageIdentifier !== 'string' || imageIdentifier.length === 0) {
              throw new Error(
                  '`imageIdentifier` must be a non-empty string, was "' + imageIdentifier + '"' +
                  ' (' + typeof imageIdentifier + ')'
              );
          }
  
          options = options || {};
  
          return new ImageUrl({
              baseUrl: this.getHostForImageIdentifier(
                  imageIdentifier,
                  options.usePrimaryHost
              ),
              path: options.path,
              user: this.options.user,
              publicKey: this.options.publicKey,
              privateKey: this.options.privateKey,
              imageIdentifier: imageIdentifier
          });
      }
docs: Get URL for the image resource
  
  @param  {String} imageIdentifier
  @param  {Object} [options]
  @return {Imbo.ImageUrl}