Leaderboard styling

A couple niggling issues:

* Rows don't move until *after* firebase gets back to us. Feels really laggy. Admittedly, that may
  only matter for the debugging behavior.

* Reordering multiple focus rows looks pretty bad (overlapping shadows, too much movement to track).

* The bounce animation doesn't work on the first change to a row. Haven't been able to track down why.

* Rank fading/restoring feels awkward.