Modified Penny Arcade logic

Instead of just scraping the page, this now does the following:

- Fetches the feed.
- Loops through the feed for the first item where the title begins with
  "Comic: ".
- Fetches the page referenced by that item's link element.
- Scrapes that page for the comic.

This is much more robust.
Merge branch 'hotfix/penny-arcade-via-feed'