* Improve arc-green code colors
This should fix all previous colors that had too few contrast on the
background. I took solarized-dark as a baseline and did various
improvments. I removed bold/italic flags because I don't think they
fit and generally other tools also don't use those font flags.
* diff tweak
* Server-side syntax hilighting for all code
This PR does a few things:
* Remove all traces of highlight.js
* Use chroma library to provide fast syntax hilighting directly on the server
* Provide syntax hilighting for diffs
* Re-style both unified and split diffs views
* Add custom syntax hilighting styling for both regular and arc-green
Fixes#7729
silverwind
mrsdizzie