def digest_for(entry)      
      MD5.hexdigest( [ entry.title, entry.content, entry.date_published ].join )
    end
def digest_for(entry)      
      MD5.hexdigest( [ entry.title, entry.content, entry.date_published ].join )
    end
Computes a unique signature for the FeedNormalizer::Entry object given.
 This signature will be the MD5 of enough fields to have a reasonable
 probability of determining if the entry is unique or not.