code: function(options) {
          options = options || {};
  
          return this.append([
              'thumbnail:width=' + (options.width || 50),
              'height=' + (options.height || 50),
              'fit=' + (options.fit || 'outbound')
          ].join(','));
      }
docs: Create a thumbnailed version of the image
  
  @param  {Object} [options]
  @param  {Number} [options.width=50]     Width of the thumbnail
  @param  {Number} [options.height=50]    Height of the thumbnail
  @param  {String} [options.fit=outbound] Fit mode: "outbound" or "inset"
  @return {Imbo.ImageUrl}