added parsed_tweet.get_unshortened_domains method and .unshortened_domains attribute
changed parsed_tweet.unshortened_urls method to .get_unshortened_urls to avoid confusion with .unshortened_urls attribute
added requirements.txt
deleted tools/django_config because it was empty
deleted tools/parsed_tweet because it was an obsolete copy of parsed_tweet
deleted tools/unshorten because parsed_tweet.get_unshortened_urls is simpler and easier.