Instead of manually redefine the route for the action, retrieve it from the routes of the application.

#### Description

Instead of manually redefine the route for the action, retrieve it from the routes of the application.
This enable also to have only place where to maintain the routing.

#### Example:

Instead of defining the name, HTTP verb, and route of the action.
```
api :POST, "/users", "Create user"
```

You could now just define the name of the action.
```
api 'Create user'
```
HTTP verb and route will be retrieved from the routes of the application.

I wonder if the `routes_path_formatter` (or `routes_formatter`) shouldn't be a class/object, that would take the array of routes and return the array of the {path: path, verb: '...'}. The reason is the case, whe you would like for some reason for example change the order of api keywords.

What about the default formater class similar to this:

```
class RoutesFormater
  def format_paths(paths)
     paths.map { |path| format_path(path) } 
  end

  def format_path(path)
     { path: "", verb: "" }
  end
end
```

It would allow to:

1. customize the order of the routes if needed
2. skip some routes from getting to the documentation
3. add things like automatic description of the api, if needed

What do you think?