Ensure we can call wire steps as nested ruby steps

[tooky]

e.g.

Given /a ruby step/ do
  step "a step on the wire server"
end

[mattwynne]

From #45 it looks like this doesn't work. It's not a big problem for users but it's a reflection of a lack of conceptual integrity in the way we load and query for step defs.

[aurelien-reeves]

It seems nested steps are suggest to discussion: cucumber/cucumber-ruby#1362

Maybe not supporting this in wire is not that bad?

[mattwynne]

It's not that bad, from a user point of view. This ticket has sat here for six years and nobody's upvoted it, or raised a bug about it.

However, it is interesting, as I think it reveals something ugly around how nested steps are currently implemented in Cucumber, otherwise they would "just work" they way you'd expect.