Change to gocomics-scrape.py & New dilbert-scrape.py 

1. Minor change to key item_link off 'guid' rather than 'origLink'. Some GoComics feeds -- e.g., http://feeds.feedburner.com/uclick/sunny-street.xml -- lack the former, but all Feedburner feeds have the latter. 

2. Created dilbert-scrape.py. Comic image lacks class to key from, so had to create a new do_img routine.