Allow to pass any command line option (or none) to the IPynb application...

Hi,

Here is a small modification to allow to pass any command line option (or none) to the underlying IPynb application.

    ./manage.py shell_ipynb --NotebookApp.ip='*'
    ./manage.py shell_ipynb --NotebookApp.open_browser=False


Note that it still works without any CLI option.

regards,