Document changes in #7968
Merge pull request #9317 from balexand/patch-1

Document changes from #7968 in Upgrading Guide
Merge pull request #9318 from steveklabnik/router_headings

Add headings to rake routes table
Add message when you have no routes defined.

Print a message in both `rake routes` and at GET "/rails/info/routes"
that lets you know you have no routes defined, as well as linking to the
Rails Guide on the topic.