FIX define_i18n_url_helper with Rails 4.2

Hi,

I just discovered that this gem wasn't working anymore with Rails 4.2.
I figured out that the problem was that the @module variable isn't present anymore in ActionPack NamedRouteCollection class. There is now two separated variables.

Regards,
Steve
Indent `when` as deep as `case`.<br>Prefer double-quoted strings unless you need single quotes to avoid extra backslashes for escaping.