Use pathlib instead of os.path where applicable (#112)

* Use pathlib in test_creation.py

* Use pathlib for PROJECT_DIR example in make_dataset.py

* Add pathlib2 for backwards compatibility if project is Python 2

{{ cookiecutter.repo_name }}/requirements.txt

@@ -8,3 +8,8 @@ coverage
 awscli
 flake8
 python-dotenv>=0.5.1
+{% if cookiecutter.python_interpreter != 'python3' %}
+
+# backwards compatibility
+pathlib2
+{% endif %}

{{ cookiecutter.repo_name }}/src/data/make_dataset.py

@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
-import os
 import click
 import logging
+from pathlib import Path
 from dotenv import find_dotenv, load_dotenv
 
 
@@ -21,7 +21,7 @@ if __name__ == '__main__':
     logging.basicConfig(level=logging.INFO, format=log_fmt)
 
     # not used in this stub but often useful for finding various files
-    project_dir = os.path.join(os.path.dirname(__file__), os.pardir, os.pardir)
+    project_dir = Path(__file__).resolve().parents[2]
 
     # find .env automagically by walking up directories until it's found, then
     # load up the .env entries as environment variables