Update mkdocs to the latest

[davidfischer]

This does a few smaller changes to mkdocs:

• Updates mkdocs to the latest version 0.17.3
• cat mkdocs.yml so it appears in the build logs like conf.py. This should make issues with MkDocs easier to debug.

In the 0.17.0 version of MkDocs, there were some changes to how themes are configured. Essentially previously, there was a theme setting and a theme_dir setting in the mkdocs.yml. Now there is a theme setting which is a dict with name, custom_dir, and other settings. We need to support both of these in the event they are building with an older version of mkdocs by pinning it in their requirements.

Should fix #3991.

[agjohnson]

What's the status of mkdocs search on RTD with a modern version?

[davidfischer]

I don't know exactly. Was it not working before?

MkDocs (the project) is built with a recent version and here are the search results: http://mkdocs.readthedocs.io/en/stable/search.html?q=something

[PowerKiKi]

Search was indeed not working and a workaround was to inject javascript. For the record, the workaround was also implemented in PHPOffice/PhpSpreadsheet@5df6680. And PhpSpreadsheet also suffers from the broken edit link in the header (#3991). If this PR can solve both issues, that would be awesome.

[stsewd]

Maybe this is solved here? (or maybe to consider) #3174

[ericholscher]

@stsewd did you test your other PR (#4184) with this version of mkdocs to confirm? I think we can probably merge this, but might have some support fallout from stuff we weren't doing in a smart way. This is just the default though, so users might already have upgraded.

[stsewd]

I was following the latest docs from mkdocs so I think shouldn't be a problem. I no quite understand the rest of your comment. After this is merged, I can rebase and overlap with the other feature, also add more tests for mkdocs there :)

[ericholscher]

Great, let's go ahead and ship it then :)