Document problem in the form of a readme.
Setup basic example where spec does not fail.

This basic example includes a basic routes file, and a basic presenter
which makes use of the application's route helpers.
Modify example to demonstrate issue.

The example Presenter does not raise, until you introduce the
`constraints option into routes file at which point an `ArgumentError`
is raised[1].

https://github.com/rails/rails/blob/master/actionview/lib/action_view/helpers/url_helper.rb#L38