SIGSEGV

Hello, I have been working on this for a week, and finaly create a repo [nua](https://github.com/lucklove/nua). It's basically a copy of Selene. It seems work when I use full userdata...

@AnonymousProgrammerLandau You are right, I use std::reference_wrapper and T to distinguish reference and value(just like the use of std::bind). It's hard to guess whether user want to use reference(T&), const...

@AnonymousProgrammerLandau Thanks for your patient. If while user need a value of type T, we only check if T is at the top of lua stack, and while user need...

@daedric Hello, I test your code in both selene and nua, the result is that it print out ``` obj1 obj2 obj2 ``` in selene, and print out ``` obj1...

@daedric The use of nua is basically the same with selene, to make you clear, I post a english version [readme](https://github.com/lucklove/nua/blob/master/ENGLISH-README.md). Note that I cut out some of the features...