Factor out jekyll-load and jekyll-prep

The custom (janky) plugin was refactored into two simple plugins, [jekyll-load](https://github.com/gregoryjscott/jekyll-load) and [jekyll-prep](https://github.com/gregoryjscott/jekyll-prep). 

* Custom plugin was deleted.
* Two plugins are now referenced in a Gemfile in a Jekyll plugins group.
* Prep scripts were added that order the data appropriated and add a few fields for display. The will allow the templates to be more generic since they will no longer need to contain logic such as sorting.