Can't find PerRequestLifetimeManager class in Unity.MVC4 or Unity(3.0)

I am trying to locate PerRequestLifetimeManager. In MSDN, it says that it is part of the Unity 3 assembly.

I've installed Unity.Mvc4 via Nuget. The package.config says I am using Unity 3.0:

The Microsoft.Practices.Unity.dll says I am using Unity 3.0

I looked inside the DLL using object browser, and the PerRequestLifetimeManager is no where to be found.

Am I missing something here?

If someone will suggest an alternative class, I am planning to use a custom PerRequestLifetimeManager found here (if I am unable to find the class).

EDIT:

I've uninstalled Unity.Mvc4 and directly installed the Unity3.0 in the package console, here is what I got:

PM> Install-Package Unity -version 3.0.1304.1
'Unity 3.0.1304.1' already installed.
Successfully added 'Unity 3.0.1304.1' to RedLions.Presentation.Web.

I still can't find the PerRequestLifetimeManager class, even in the official library.