3686 Extra padding on fandom tags in work blurbs when in a listbox

http://code.google.com/p/otwarchive/issues/detail?id=3686

We were trying to put padding around the listbox heading (that is, where it says "Recent works") but didn't get specific enough in the CSS, so it was affecting all things with that class.

With bonus removal of `margin-top: 0`, since `margin: 0` includes the top margin.
That's a really good question to which I do not know the answer. It's basically the difference between the color of "orphan_account" in these two screen shots:
![current_selector](https://cloud.githubusercontent.com/assets/907055/3276952/ca461824-f357-11e3-95eb-027bb27bb31d.png)
![direct_child_selector](https://cloud.githubusercontent.com/assets/907055/3276953/ca49670e-f357-11e3-8db2-a69ccee49666.png)
The top one is the current situation (darker grey) and the bottom one is what it looks like if I chang it to `.listbox > .heading a:visited` (lighter grey). I'm not sure if the darker grey was an intentional choice or not (maybe something to do with the various shades of blue in the background?), since it predates me.