External data directory support

[robertmuehsig]

The commits are kinda annoying... maybe we could use this: https://github.com/18F/jekyll-get

[robertmuehsig]

But then we need this: https://ayastreb.me/deploy-jekyll-to-github-pages-with-travis-ci/

[robertmuehsig]

https://docs.travis-ci.com/user/deployment/pages/

[robertmuehsig]

deploy:
provider: pages
repo: robertmuehsig/ghpages-demo
target-branch: master
skip-cleanup: true
github-token: $GHKey # Set in the settings page of your repository, as a secure variable
keep-history: false
on:
branch: master