So here we could either do
```
    >>> with open(os.path.join(here, 'gtimelogrc.vm0300')) as fp:
    ...     settings = Settings(fp)
```
or maybe
```
    >>> settings = Settings(StringIO('''
    ... [gtimelog]
    ... virtual_midnight = 02:00
    ... '''))
```
which I prefer to having a bazillion real config files scattered around the tests directoy.

If multiple tests need the same config file, we could define it at the module level and reuse.