Correctly set URL and path for requests to WCF services whose base URIs do not have trailing slashes

@thecodejunkie and I found an issue in the Nancy WCF integration during a recent debugging session. If the service's base URI did not have a trailing slash, such as http://localhost:1234/base, a request to "/test/stuff" caused NancyWcfGenericService to incorrectly set the Nancy URL to http://localhost:1234/base/base/test/stuff.

This fix ensures the Nancy URL is correctly set to http://localhost:1234/base/test/stuff when the base URI has no trailing slash.