@Override
    public <B, V> V acceptExtensionVisitor(
            BindingTargetVisitor<B, V> visitor,
            ProviderInstanceBinding<? extends B> binding) {
        return visitor.visit(binding);
    }
This is needed for 'initialize(injector)' below to be called so the provider
can get the injector after it is instantiated.
ribbon-guice/src/main/java/com/netflix/ribbon/guice/RibbonResourceProvider.java