- Tasks blocking xmonad 0.1
    - Move the multi-screen handling from XState to StackSet
    - Fix the missing windows on workspace switch bug

- Clean up focus and mouse related issues.  During 'refresh', xmonad should
  ignore EnterNotify events (by changing selectInput for the duration).
- let mod+enter demote a master window

- Xinerama bugs:
    - Closing the last window in a workspace moves focus to another Xinerama
      screen.
    - Focus goes to other Xinerama screen when changing to empty window and
      create new window.
    - Focus doesn't always follow mouse or mouse click across Xinerama screens;
      sometimes focus will only switch with key command to switch to that
      screen.

- 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.