Update nbsphinx to 0.6.1

[pyup-bot]

This PR updates nbsphinx from 0.5.0 to 0.6.1.

Changelog

0.6.1

* ``.ipynb_checkpoints`` is automatically added to ``exclude_patterns``

0.6.0

* Thumbnail galleries (inspired by https://sphinx-gallery.github.io/)
* ``nbsphinx-toctree`` as cell tag
* Keyword arguments in ``nbsphinx_custom_formats``
* Python 2 support has been dropped

0.5.1

* This will be the last release supporting Python 2.x!
* Support for https://github.com/choldgraf/sphinx-copybutton
* Executed notebooks are now saved in the HTML output directory

Links

• PyPI: https://pypi.org/project/nbsphinx
• Changelog: https://pyup.io/changelogs/nbsphinx/
• Docs: https://nbsphinx.readthedocs.io/

[pyup-bot]

Closing this in favor of #196