code: function trending () {
  
      var language;
      var timespan;
      var callback;
  
      if (arguments.length === 3) {
          language = arguments[0];
          timespan = arguments[1];
          callback = arguments[2];
      }
      else if (arguments.length === 2) {
          language = arguments[0];
          callback = arguments[1];
      }
      else {
          callback = arguments[0];
      }
  
      language = (language || 'all').toLowerCase();
      timespan = timespan || 'daily';
  
      function onResponse (err, html) {
          var repositories;
  
          if (err) {
              return callback(new VError(err, 'failed to fetch trending repositories (language: %s).', language));
          }
  
          repositories = scraper.repositories(html);
  
          callback(null, repositories);
      }
  
      mandatory(callback)
          .is('function', 'Please define a proper callback function.');
  
      request(endpoint, { l: language, since: timespan }, onResponse);
  }
docs: Grabs the trending repositories of a particular language.
  
  @param {string} language
  The language for which the trending repos should be fetched.
  
  @param {function} callback
  Will be invoked when the trending repository
  data has been fetched. Invoked as `callback(err, repositories)`.