Update references to non-Python files

[forsyth2]

Update references to non-python files. In #36, using importlib.resources.path was discussed. While it is not strictly required, it is the preferred method.

Replace templateDir = os.path.join( os.path.dirname(__file__), 'templates' ) in zppy/__main__.py with something like https://github.com/MPAS-Dev/compass/blob/864ebf7425d5f076d4c18673b43d102308da7071/compass/landice/tests/enthalpy_benchmark/B/__init__.py#L44-L46:

from importlib.resources import path
[...]
        with path('compass.landice.tests.enthalpy_benchmark', 'README') as target:
            symlink(str(target), '{}/README'.format(self.work_dir))