code: function(options) {
          var params = [];
  
          if (options.width) {
              params.push('width=' + toInt(options.width));
          }
  
          if (options.height) {
              params.push('height=' + toInt(options.height));
          }
  
          if (!params.length) {
              throw new Error('width and/or height needs to be specified');
          }
  
          return this.append('maxSize:' + params.join(','));
      }
docs: Resize the image to be at most the size specified while still preserving
  the aspect ratio. If the image is smaller than the given size, the image
  remains unchanged
  
  @param  {Object} options
  @param  {Number} [options.width]  Max width of the image
  @param  {Number} [options.height] Max height of the image
  @return {Imbo.ImageUrl}