[MINOR FEATURE REQUEST]
1) You have a list of file types NOT to add favicons next to. That may be something nice to have in the settings, rather than a code change, since i needed to add one.
2) If you start CACHEing in V0.3, you may need to also add a "clear cache" option.
3) I am not sure how you check if a link is to a local page or not? I have a link on my REAL hompage (joshua.hailpern.com) which is to /news-updates, yet it is viewed as being an external link. Not sure if this is international or not... (this is so minor)
4) So while you are just using Google for favicons, when a cite doesn't have an icon, it returns that globe thing. I like this. But others may not. You may want to add a check box in the settings along the lines of "if there is not favicon found, use google default, or specify a default icon."
But really man, this is a fantastic plugin that makes me super happy and glad to use.