code: function(options) {
          if (!options || isNaN(options.angle)) {
              throw new Error('angle needs to be specified');
          }
  
          var bg = (options.bg || '000000').replace(/^#/, '');
          return this.append('rotate:angle=' + options.angle + ',bg=' + bg);
      }
docs: Rotate the image by the specified angle
  
  @param  {Object} options
  @param  {Number} options.angle Angle to rotate by
  @param  {String} [options.bg]  Background color of image, in hex-format
  @return {Imbo.ImageUrl}