Unity 5 Fix

[Dharengo]

I hope I'm doing this right, I'm quite new to github. Anyway, a modificaction was made to mythgarr's version of Spriter2Unity to make it compatible with Unity 5, and and since your version is the "newest" one, I thought to use this method to notify you.

That said, you might need to keep the Unity 4 version around for people who still use Unity 4. Idk how this works exactly but you should be able to make it work somehow.