(Bug 3523) CSS tweaks for ContextualPopup

- apply float to .Userpic instead of .Userpic img, so that it looks
  right if we're applying color to .Userpic

- make sure .ContextualPopup can always contain .Userpic

- fix typo: 9 => 0
Merge pull request #192 from afuna/contextual-css-tweaks-bug3523

(Bug 3523) CSS tweaks for ContextualPopup