code: function getByFirstImage(file, attributes) {
    var $ = cheerio.load(file.contents.toString()),
      img = $('img').first(),
      obj = {};
    if (img.length) {
      _.forEach(attributes, function(attribute) {
        obj[attribute] = img.attr(attribute);
      });
      return obj;
    } else {
      return undefined;
    }
  }
docs: retrieve cover from file object by extracting the first image
  
  @param  {Object} file file object
  @return {Object}       cover