fix cookiecutter id

{{ cookiecutter.package_name }}/src/{{ cookiecutter.package_slug }}/__init__.py

-from {{ cookiecutter.package_name }}.main import main
+from {{ cookiecutter.package_slug }}.main import main
 
 __all__ = ['main']

{{ cookiecutter.package_name }}/tests/test_main.py

 """Sample test module."""
 
-from {{cookiecutter.package_name}} import main
+from {{ cookiecutter.package_slug }} import main
 
 
 def test_main():