Update to Jekyll 3 and rouge crystal highlighter

[bcardiff]

• Some technical dept and move to rouge crystal highlighter.
• Meanwhile, update ruby to latest stable version,
• Add livereload to docker-compose.
• In order update rouge I needed to remove github-pages (there was a strict version dependency).
• A 'jekyll-assets', '~> 2.4.0' was needed in order to avoid some compilation issues.

I only update the most recent post and homepage snippets to use the new highlighter.

If updating your working environment run:

$ rm -rf .asset-cache/ _site/

Fixes #65 and keeps me happier with live reloading and the new highlither