DOC: Change a few URLs to https

Author: mgeier

doc/usage.ipynb

@@ -283,7 +283,7 @@
     "  [example](https://nbsphinx.readthedocs.io/en/better-theme/),\n",
     "  [usage](https://github.com/spatialaudio/nbsphinx/compare/better-theme^...better-theme)\n",
     "\n",
-    "* [bootstrap](http://sphinx-bootstrap-theme.readthedocs.io/):\n",
+    "* [bootstrap](https://sphinx-bootstrap-theme.readthedocs.io/):\n",
     "  [example](https://nbsphinx.readthedocs.io/en/bootstrap-theme/),\n",
     "  [usage](https://github.com/spatialaudio/nbsphinx/compare/bootstrap-theme^...bootstrap-theme)\n",
     "\n",
@@ -350,7 +350,7 @@
     "\n",
     "* https://github.com/kynan/nbstripout\n",
     "* https://github.com/toobaz/ipynb_output_filter\n",
-    "* http://tillahoffmann.github.io/2017/04/17/versioning-jupyter-notebooks-with-git.html\n",
+    "* https://tillahoffmann.github.io/2017/04/17/versioning-jupyter-notebooks-with-git.html\n",
     "* http://timstaley.co.uk/posts/making-git-and-jupyter-notebooks-play-nice/\n",
     "* https://pascalbugnion.net/blog/ipython-notebooks-and-git.html\n",
     "* https://github.com/choldgraf/nbclean\n",

src/nbsphinx.py

@@ -20,7 +20,7 @@
 
 """Jupyter Notebook Tools for Sphinx.
 
-http://nbsphinx.readthedocs.io/
+https://nbsphinx.readthedocs.io/
 
 """
 __version__ = '0.4.2'