addSlide: clone have the "active-slide" class 

Due to the new feature addSlide(obj,pos), the setup() method can be call multiple time.
The first time the slides are initialized, the first/last slide are cloned THEN the namespace+"active-slide" is set.

then addSlide() is call during customer part execution.

Setup is call again, the first/last slide are cloned again.
but this time clone keep the "active-slide" class.
And you have mulitple "active-slide"

Patch : 
Simply remove the class for the 2 clones