Make InjectionTransientLifetimeManager public

`InjectionTransientLifetimeManager` is the only LifeTimeManger which class is made internal.
By making it public, people like use who use your library to extend upon can also make use of it.

Author: cduivis

src/Lifetime/InjectionTransientLifetimeManager.cs

@@ -8,7 +8,7 @@ namespace Unity.Microsoft.DependencyInjection.Lifetime
     /// except it makes container remember all Disposable objects it created. Once container
     /// is disposed all these objects are disposed as well.
     /// </summary>
-    internal class InjectionTransientLifetimeManager : LifetimeManager, 
+    public class InjectionTransientLifetimeManager : LifetimeManager, 
                                                        IFactoryLifetimeManager,
                                                        ITypeLifetimeManager
     {
@@ -38,4 +38,4 @@ public override bool InUse
 
         #endregion
     }
-}
+}