Add a binding parameter to Camping.goes to allow for Camping-based modules within namespaces

Exactly what is says on the tin.

Please refer to an docs for Camping.goes for an example, or just look at [MatmaRex/mrowka/web.rb:23](https://github.com/MatmaRex/mrowka/blob/master/web.rb#L23) for a kind-of real-world example.