[dwm] dmenu directory test

I just cloned the latest tip for dwm and dmenu. I'm happy to report
everything is working great for me. On that note, I was wondering if it
would make sense to add a test in dmenu_path to make sure the directory
actually exists before trying to cd into it? I know I have $HOME/bin in
my $PATH, but on my current machine I don't have that directory created.
Attached is a simple tweak to dmenu_path to test if the directory
exists. Thanks.

-- 
James Turner
BSD Group Consulting
http://www.bsdgroup.org