~/.xmonad: Make zenity windows floating.

I use them for various notifications (obnoxious ones).

.xmonad/xmonad.hs

        manageHook = composeAll [
                        className ?? (\cn -> any (cn ==) ["Skype", "Pidgin", "Geary"]) --> doF (W.shift "3"),
                        className =? "Exe" --> doFullFloat,
                        className =? "Zenity" --> doFloat,
                        manageSpawn,
                        manageDocks,
                        fullscreenManageHook