Pretty print handler names

[airhorns]

This replaces and closes #138, closes #144.

This adds a handler function's name to the pretty printed route output. It uses Function.name, so no new dependencies or anything.

Before:

└── /test (GET)
    └── /hello
        ├── /
        │   └── :id (GET)
        │       :id (POST)
        └── world (GET)

After:

└── /test (GET testRoot)
    └── /hello
        ├── /
        │   └── :id (GET getHello)
        │       :id (POST postHello)
        └── world (GET helloWorld)

It required a kind of annoying change in how the handlers are iterated to pretty print, but that change is also necessary for the constrained route handler work in #166 so it's one more thing that I peeled out for merging separately.

[airhorns]

@delvedor are you the right person to review this? It's good to go!

[mcollina]

lgtm

[mcollina]

Yes, @delvedor is the right person.

[airhorns]

@delvedor would love to get your feedback on this!

[airhorns]

The work here has been merged in #170 so I am going to close this!