~/.xmonad: Spawn sakura w/ tmux as terminal.

This makes me (sometimes happy), gives me a few potentially nice things,
for now mostly just proper titles for terminals.

.xmonad/xmonad.hs

    dbusClient <- connectSession
    xmonad $ defaultConfig {
        modMask  = mod4Mask,
        terminal = "sakura",
        terminal = "sakura -x tmux",
        -- Ignore docks (via some WM_* attribute?)
        manageHook = composeAll [
                        className ?? (\cn -> any (cn ==) ["Skype", "Pidgin", "Geary"]) --> doF (W.shift "3"),