In Spina 1, when instantiating a Spina-wrapped class, the wrapper would

return an instance of the wrapped class, rather than the wrapper. The

aim was to get as close as possible to returning the defined class.

However, this had issues:


Consumers couldn't do instanceof checks against the class, because

   the wrapped class's instance would never be an instance of the

   wrapper.


Operations on the wrapper's prototype wouldn't apply to the wrapped

   class's prototype, and this would break things like Jasmine spies or

   any operations that needed to deal with instances or state on

   prototypes.


It just generally made it confusing, having MyClass and

new MyClass() being very different things.


Ultimately, there's no reason to avoid returning an instance of the

wrapper class. This change updates the logic so we're always getting an

instance of the class the caller constructed.
This shouldn't negatively impact any callers, but it is a big enough

change in behavior that we're calling this Spina 2.0. (More

potentially-breaking changes are also coming).

Tested this in Review Board, along with some upcoming changes, and

verified all tests passed.
Manually tested construction of wrapper classes, making sure that

the instances were in fact instances of the wrapper class and not the

wrapped class.