Recurse over directory paths

[mcandre]

Automatically recurse over any directory paths supplied, so that editorconfig-tools can run over large projects, without resorting to UNIX find tricks, which are fragile.

Globstar is not a solution: This requires users to use glob-enabled shells (breaking many WIndows shells), and furthermore requires careful crafting of path globs to actually recurse (./* is only toplevel, for example).