Installing Jekyll

Assumes jekyll 3.8.4 per Repo 5th November 2018

* install rbenv and ruby per https://jekyllrb.com/docs/installation/macos
* gem install bundler
* bundle install
* gem install jekyll -v 3.8.4
    * this step only necessary because bundle install provides jekyll but appears to not provide a shim for it correctly
    * reinstalling as the gem with targeted version then provides the shim