Added container registration for Func<IRouteCache>.

StructureMapNancyBootstrapper.GetDiagnostics(), which overrides NancyBootstrapperBase.GetDiagnostics() throws an exception because StructureMap doesn't know how to handle the Func<IRouteCache> parameter on the DefaultRouteCacheProvider constructor.  StructureMap tries to resolve Func<IRouteCache> when injecting constructor dependencies for Nancy.Diagnostics.DefaultDiagnostics.