Mix task that prints all defined routes in nice human readable format

Task is run with `mix weber.routes`.

It prints routes with following formatting:

```console
➜  trash git:(master) ✗ mix weber.routes
   GET  /                             Elixir.Trash.Main#index
   GET  /trash/bins                   Elixir.Trash.Bins#index
   GET  /trash/bins/new               Elixir.Trash.Bins#new
  POST  /trash/bins                   Elixir.Trash.Bins#create
   GET  /trash/bins/:id               Elixir.Trash.Bins#show
   GET  /trash/bins/:id/edit          Elixir.Trash.Bins#edit
   PUT  /trash/bins/:id               Elixir.Trash.Bins#update
DELETE  /trash/bins/:id               Elixir.Trash.Bins#destroy
```

It's still work in progress, but feedback is of course welcome. Following things still need to be done: column titles, dynamic column sizes, handling of redirect routes and `Elixir.` needs to be removed.