dmenu exits with code 1 when you hit Escape, and I wanna create a contrib that
takes advantage of that.
This required changes in four contribs (Commands, DirectoryPrompt, ShellPrompt,
and WorkspaceDir), and might require changes in users' Configs. Also, I'm not
sure some of the changes I made to the client code are very Haskelly. Would
appreciate input there.
Just a small refactooring (well, now runCommand requires a command list, and
I added runCommand's that will take a string to run it against the default
command list) to include this module in MetaModule so that we can track it
in case of API changes (this patch has been requested by Spencer).
