Deferred commands are not routed

[jonsequitur]

When scheduling a deferred command, it's intuitive to do this:

var submitCode = new SubmitCode("// some code", "csharp");
Kernel.Root.DeferCommand(submitCode);

This actually defers the command against the Root (CompositeKernel) which then doesn't appropriately route it to the CSharpKernel.