- using the scrollwheel in the TabBar used to scroll the document:
  - even though the deck next to it handles scroll event on its own
  - thus there are two areas that arent even touching (separated by the
    deck) scrolling the same area
- instead, now we capture mousewheel scrolls and switch through the
  decks of the sidebar. This should also severely simplify navigating
  them.

Change-Id: Ie2136f4ec67dedf72ff6b56d16356f6a12de74ea