- tasks before 0.1:
    - Code clean up after tiling and StackSet changes
    - Make sure the quickchecks make sense with the new StackSet

- think about the statusbar/multithreading.
    Three shared TVars:
        windowTitle :: TVar String
        workspace   :: TVar Int
        statusText  :: TVar String
    Three threads:
        Main thread, handles all of the events that it handles now.  When
        necessary, it writes to workspace or windowTitle

        Status IO thread, the algorithm is something like this:
            forever $ do
                s <- getLine
                atomic (writeTVar statusText s)

        Statusbar drawing thread, waits for changes in all three TVars, and
        redraws whenever it finds a change.

- tiling:
    - Layout calculation: the current algorithm is crude, windows overlap
    - make focus remain between workspace switches
    - change focus in the StackSet structure on EnterNotify
    - let mod+enter demote a master window
    - borders (low priority, maybe wait until 0.2)
    - let focus-follows-mouse also change the active workspace (not just the
      active window); note that this currently also makes click-to-focus appear
      slightly buggy, since sometimes, the wrong window is exempted from setButtonGrab

* Tile vertically/ resize height.