Make ls output respond to width of terminal

[nfischer]

We can improve ls().inspect() by making it format output like:

$ ls
file1.txt   file2.txt   file3.txt

Instead of putting newlines between all of them. Output would break on word boundaries once the entire column-width is taken up. Cash has an implementation of this in its ls command.

[nfischer]

We may be able to detect if it's coming from ls output by checking Array.isArray(this)