Fix an issue where Journey was failing to clear the named routes hash when the
routes were reloaded and since it doesn't overwrite existing routes then if a
route changed but wasn't renamed it kept the old definition. This was being
masked by the optimised url helpers so it only became apparent when passing an
options hash to the url helper.
Move the Journey code underneath the ActionDispatch namespace so
that we don't pollute the global namespace with names that may
be used for models.
Fixesrails/journey#49.