Added JsTestCore::Resources::Specs::Spec.spec_resource_class and spec_resource_class= so it can be overridden.
Added JsTestCore::Resources::Specs::Spec.spec_resource_class and spec_resource_class= so it can be overridden.

pivotalexperimental/js-test-core,pivotalexperimental/js-test-core,pivotalexperimental/js-test-server,pivotalexperimental/js-test-server