Enhance expressiveness of Path

Hello guys!

Thank you for this useful lib.

Inspired by [Python's 3.4 new pathlib](https://docs.python.org/3/library/pathlib.html), I made this change that allow us to change:

```python
BASE_DIR = Path(os.path.dirname(os.path.dirname(__file__)))

TEMPLATE_DIRS = (
    BASE_DIR.parent.child("templates"),
)
```

As

```python
TEMPLATE_DIRS = (
    BASE_DIR / ".." / "templates",
)
```