Fix bug reported in #66

The `copy_support_files` function was not accounting for filepaths that
contain spaces or other invalid characters, hence when trying to run
make_emperor.py and setting the output path to something like
`/Users/jappleseed/data/oct 12/` would fail because of the `oct 12`
component in the path.

A new test has been added to `test_util.py`.

Fix #66