Umbrella Apps - What are they and Why/How are they Useful?

## "Umbrella apps enable multiple child applications to run together, which can help to reduce the overall complexity of our app by separating different functionality into smaller apps that run together."

Intro: http://www.phoenixframework.org/docs/configuration#section-umbrella-apps

## Background Reading / Watching

+ Shattering your application into an umbrella project by Luke Imhoff (Lonestar ElixirConf 2017): https://youtu.be/1ocF_9Nc0ik
+ Building Umbrella Project by Wojtek Mach (ElixirConf 2016): https://youtu.be/6NTmUQClHrU
+ Heroku deployment of Umbrella Apps: https://medium.com/@robinsjdotcom/checklist-for-deploying-umbrella-applications-to-heroku-74a79e07e21f
+ Create umbrella app and deploy with distillery:
https://medium.com/@brucepomeroy/create-an-elixir-umbrella-project-containing-a-phoenix-app-and-build-a-release-with-distillery-46371f2617df

## Todo:
+ [ ] Create an _example_ umbrella app to showcase this functionality.