WIP: Resolve "Enable Jekyll's Syntax Highlighting with Rouge"

These are the steps so far:

• add which syntax-highlighter to use in _config.yml
• add gem for rouge in Gemfile
• do a gem update with bundler
• use rougify to create style: rougify style monokai.sublime > syntax.css
• import syntax.css in main.css
• edit a page with highlight tag and a code snippet
• build and serve jekyll page

Styles can be found here: https://jwarby.github.io/jekyll-pygments-themes/languages/ruby.html

Closes #29 (closed)