Add headings to rake routes table

Another "get some feedback on this idea" PR. Thanks @burtlo!

It's easy to forget what the order of things are in the routing table, especially if you're new. The HTML view has headings, but the console does not. They're a little different at the moment due to space, but I can change them to be as close to possible once we determine this is a good idea.

One other thing I'd like to implement, but haven't: test if we're running in a shell or not. If we're not, then we shouldn't print the headings. If you're writing scripts that rely on the output of the task, no headings is way better.