Update Hub documentation to stand up another Hub

[melodykramer]

Quite a lot of documentation exists to stand up a version of the Hub:

https://hub.18f.gov/101/go/index.html
https://hub.18f.gov/101/index.html
https://hub.18f.gov/101/internal-vs-public/index.html
https://hub.18f.gov/101/rbenv/index.html
https://hub.18f.gov/101/vagrant-and-ansible/index.html

This is not up-to-date and likely needs to be reworked. Putting this here as a placeholder just to capture that these pages exist and should be looked at.