Adds dejavu

[marimeireles]

This is the first PR to introduce the Dejavu feature.
Dejavu intends to be a tool to facilitate for the Jupyter user to generate static pdf outputs for their notebooks mimicking the behavior of voilà. So, with one command line you get all the presets configured for you, generating a pdf presentation:

jupyter dejavu notebook.ipynb

I'm trying to mimic voila's results with this. For future PRs we'll probably have to change or add a new template configuration so we can have a correct pagination.
Please let me know what you think of it!

cc: @SylvainCorlay

[marimeireles]

I also have an example notebook in case you're interested in starting an example session. =)

[MSeal]

Interesting! So the intend is to mimic voila default behavior? Should we make this a template extension of reveal rather than a new App to avoid command confusion maybe?

@SylvainCorlay @maartenbreddels would like your input

[SylvainCorlay]

Voilà is really just nbconvert + live kernel and widgets except that by default, inputs and prompt numbers are hidden.

The goal of déjàvu is to provide a shortcut for nbconvert that has the same defaults as Voilà.

TemplateExporter.exclude_input = True            # Hide inputs
TemplateExporter.exclude_output_prompt = True    # Hide prompts
TemplateExporter.exclude_input_prompt = True     # Hide prompts
ExecutePreprocessor.enabled = True               # Execute notebook
WebPDFExporter.paginate = False                  # Prevent WebPDF pagination

We could not make it an alias because one should be able to overwrite these options (like in the case of Voilà).

I am not sure if we should default to HTML or WebPDF.

[marimeireles]

I am not sure if we should default to HTML or WebPDF.

So Sylvain and I were talking about this and we got in an agreement that's better to generate an html file so it exhibits the exact same result as voila. Even though pdf seems like a more useful format it produces a different less elegant result than when converted to html.

[MSeal]

Alright sounds reasonable to me. There's a doc build issue seems unrelated to this PR. There's been some issues with the new version of Sphinx that were unresolved last time I checked that we were working around.

[marimeireles]

Thanks @MSeal, soon I'll also be publishing a blog post that talks a bit about it + nbconvert! :)

[MSeal]

Great! I think if we can also address #1401 this week we should do a patch release with the changes this weekend so they're available to others.