Latest `highlight.js` node module breaks the build

[JesseBuesking]

Description

Fails to build with latest hightlight.js node module.

How to reproduce

Get the latest highlight.js and run python setup.py build_ui.

Fix

I looked into the commits over on highlight.js and found this commit stating

github-gist has been removed in favor of github [Jan Pilzer][]

If I update highlight.css and change

@import url('node_modules/highlight.js/styles/github-gist.css');

to

@import url('node_modules/highlight.js/styles/github.css');

everything works.

[GaetanLepage]

Thanks for giving the fix :)