~/.xmonad/xmonad.hs: Use urxvt as the default terminal.

.xmonad/xmonad.hs

main = do
    xmobar <- spawnPipe "xmobar"
    xmonad $ defaultConfig {
        modMask = mod4Mask,
        modMask  = mod4Mask,
        terminal = "urxvt",
        -- Ignore docks (via some WM_* attribute?)
        manageHook = composeAll [
                        manageDocks,