implement issue #12 (why can't I just attach this request to that issue?)

Two issues with this (I'll file them as follow-ups)
1. Using Panel asserts like crazy for some reason. This appears to be a known bug in the add-on sdk: https://bugzilla.mozilla.org/show_bug.cgi?id=811837
2. Clicking "Use Normal Window" needs to whitelist a host, really, not a URL. This should be fixed when we identify blushy sites based on hosts instead of substrings.