Cleanup css
Switch to CSS based fade in / out
Cleanup show/hide

It's important here that we changed the button selector, because before
you were binding the first button on the entire page.  It was just luck
that it happened to be the one you were looking for.

We now put `display: none` on the box when it's not being animated or
shown.  That way, it won't block things below it from being clicked
(when something is opacity 0 it can't be seen, but it can still be
clicked on).
Don't bother with IE8

We now wait until the DOM is ready to initialize.  That way, we only
have to get a ref to the suggest_box once, instead of in every scroll
event.  Also, we now use a more sane way of binding the scroll event
which won't break if anyone else on the page tries to do it.
Use document.body uniformly.  Don't error if popBox doesn't exist for some reason.