Add support for Jazz Hands

[jemerick]

Adds support for Jazzy to build docs using a custom theme that will later be pulled into the documentation portal.

Installation

[sudo] gem install jazzy

This PR is ready for review.

Risk

This PR makes no API changes, just adds a build step and requires jazzy to be installed.

Testing Plan

1. Install Jazzy
2. Build. Ensure Docs are updated to reflect any doc changes.

Summary

Add a build step for jazzy using a custom theme and include the docs in the repo.

[joeljfischer]

I've been thinking about this some more. I don't think we want jazzy to build on every SDL build, because that would extend the build times dramatically. Second, building SDL is not currently building the docs for me. I think instead there should be a scripts folder that contains a build-documentation script that can be run to generate the documentation easily and integrated into a release script eventually as well. This would mean that random branches wouldn't necessarily have the up to date docs, however I don't want to take the fairly quick rebuild times and extend them to nearly 30 seconds. That would just kill productivity. In the future, we at livio could build a commit bot that would run the documentation parser and modify commits to include it since github just released that capability.

[joeljfischer]

We could also expand Travis to build and upload these for us as well?

[joeljfischer]

Closed in favor of #417