BF: pass lists to subprocess.check_output() in launcher demo

- hopefully lists work here in python 3
- a side-benefit of using lists: automatically handles white-space in filenames
- not sure whether "if LOCALE:" needs to be "if LOCALE  is not None:" (per logic in original code). I doubt that it matters (empty list or empty string? int 0?)
Merge pull request #10 from jeremygray/master

BF: pass lists to subprocess.check_output() in launcher demo