Fix extending Namespace prototype not working on IE8

It seems IE8 is not to keen on extending prototypes in some circumstances. It spills JS errors when using the factory with namespaces on.

Not sure my solution is the best way, but it works :)
You can try it with these in **IE8**:

not working: http://codepen.io/andrefgneves/full/kBLzu
working: http://codepen.io/andrefgneves/full/DjHLC