Please document the documentation

[infinity0]

It's unclear how to build the docs. Even after I build jupyter-js-widgets, I get:

ipywidgets-6.0.0/docs$ make html
sphinx-build -b html -d build/doctrees   source build/html
Running Sphinx v1.4.9
making output directory...

Extension error:
Could not import extension jupyter_sphinx.embed_widgets (exception: No module named jupyter_sphinx.embed_widgets)
Makefile:34: recipe for target 'html' failed
make: *** [html] Error 1

Am I supposed to install jupyter-sphinx first? Can I build jupyter-sphinx by itself, without ipywidgets? Otherwise we have a circular dependency ipywidgets -> jupyter-sphinx -> ipywidgets.

[jasongrout]

CC @SylvainCorlay - I don't know how to build the docs right now either.

[jasongrout]

Found it! (and updated it...) https://github.com/jupyter-widgets/ipywidgets/blob/master/docs/source/dev_docs.md