Now unbundles exceptions from creating instances

When calling CreateInstance(), any exception being thrown will be
unbundled and returned to the test instead of the
TargetInvocationException.
Original stack traces are not lost

Ensured that the original stack trace is not lost when re-throwing
exceptions caught when constructing real instacnes.
Merge pull request #11 from EdwardSalter/master

Now unbundles exceptions from creating instances