new_contents: from comics.aggregator.crawler import CrawlerBase, CrawlerImage
  from comics.core.comic_data import ComicDataBase
  
  
  class ComicData(ComicDataBase):
      name = 'Cardboard Crack'
      language = 'en'
      url = 'http://cardboard-crack.com/'
      start_date = '2013-03-01'
  
  
  class Crawler(CrawlerBase):
      history_capable_days = 30
      schedule = 'Mo,Tu,We,Th,Fr,Sa,Su'
      time_zone = 'US/Pacific'
  
      def crawl(self, pub_date):
          feed = self.parse_feed('http://cardboard-crack.com/rss')
          for entry in feed.for_date(pub_date):
              url = entry.summary.src('img[src$="500.gif"]')
              return CrawlerImage(url)
  
subject: add crawler for Cardboard Crack