IsRegistered<T> fails for registrations on parent containers

[Cylox]

I'm using a SpecFlow runtime plugin and the RegisterGlobalDependencies event to add my own dependencies to the global SpecFlow container.
When I ask a sub-container (Feature- or ScenarioContainer) inside the test execution whether the dependency is registered through the IsRegistered call it returns always false. This is because IsRegistered only looks at the registrations of the current container, not the base container. Now the weird thing is that you can successfully call Resolve with the same interface and get the dependency. This is because Resolve will ask the base container for resolving the type if it cannot resolve the type itself whereas IsRegistered will not consult the base container.
This should be fixed by making IsRegistered also check the base container registrations.

[patrickdreyer]

Pull request #20 includes a fix for your issue.