[DC/TB] [78399060] split up routes to prevent 404 problem

To allow the /docs route to serve both the UI and the JSON, we need to create a separate path for the UI: /docs/ui
https://www.pivotaltracker.com/story/show/78399060
Yes, we want it to default to /docs from the project root - if you know a good way to reference the project root from a gem then I'm all for it.