[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
Doing that for a rails app is pretty straightforward (use a railtie to set the configuration), but not so sure how to handle a non-Rails app. Also, the railtie setup would require some changes to how this is configured, so I vote we hold off until we feel a need for it. Glad we're on the same page with defaulting to <root>/docs though.