returns an array of the directories under a given
directory, including itself
returns an array of the names of every file or directory
under a given path
It still needs a test suite. I'm probably going to do this by way of
creating a sandbox with a virtual file module implementation so I can
run various scenarios on a consistently reconstructed file system
view, without having to muddy up the disk and leave it in inconsistent
states when tests fail.
This comes out of Tom's and my experiments to assess how much of the
among CommonJS implementations.