Authorize filter read notebooks

[tanguycdls]

fix https://github.com/nteract/scrapbook/issues/81

Optional filter_path

    Parameters
    ----------
    path : str
        Path to directory containing notebook `.ipynb` files.
    path_filter: Optional[Callable[str, bool]]
        Func used to filter the notebook by its filename:
        should return True if you want to read that notebook and False otherwise

    Returns
    -------
    scrapbook : object
        A `Scrapbook` object.

[tanguycdls]

I'm getting

ERROR: could not install deps [.[dev]]; v = InvocationError("/home/travis/build/nteract/scrapbook/.tox/py36/bin/python -m pip install '.[dev]'", 1)
___________________________________ summary ____________________________________
ERROR:   py36: could not install deps [.[dev]]; v = InvocationError("/home/travis/build/nteract/scrapbook/.tox/py36/bin/python -m pip install '.[dev]'", 1)
The command "tox -e $TOXENV" exited with 1.

On python 3.6 only It does not seem related to that PR, I can try rebasing on main ? @MSeal Thanks :)

[MSeal]

Thanks for making the PR!

[tanguycdls]

Thanks :) !