Support trailing slash

[le0pard]

By #105 request.

/cc @bogdan

[bogdan]

I think we should support it in the same way as rails:

site_path(1, :trailing_slash => true)  # => "/sites/1/"

In the same way we support :anchor for example.

So I would preffer the following behaviour:

expect(evaljs("Routes.inbox_path(1, {trailing_slash: true})")).to \
  eq(routes.inbox_path(1, trailing_slash: true)})

[le0pard]

@bogdan Ok, will change this

[le0pard]

@bogdan done, support in params and default_url_options.