[xmonad] Visual hints for XMonad actions

[wagnerdm at seas.upenn.edu]

Quoting Brandon Allbery <allbery.b at gmail.com>:

> Last I checked, dzen didn't have a way to remove itself after a timeout; if

dzen2 -p 10 for a ten-second timeout. I think the real reason  
ShowWName doesn't use dzen is to avoid having an external dependency,  
which seems pretty reasonable really.

~d