Added default support to DummyValueCreationSession for type Lazy<T>

Based off of the behavior that is defined for Task. Discussed in issue #358.
Thanks for the spec. I appreciate it. The standard, though, is to name the classes when_* and have the `It`s supply the "should"s. Would you mind renaming the class? Based on some other comments I'm about to make, I might suggest something like `when_creating_a_dummy_lazy_of_t`. Let's see how that works out when we continue.