Define circle using 3 points

I have been trying to adapt some C# code as found here: http://stackoverflow.com/questions/13977354/build-circle-from-3-points-in-3d-space-implementation-in-c-or-c

..so that it can work with Unity. It compiles, however it's not working quite as expected. For instance the circle should always go through the 3 points, however it doesn't. And changing the points on the z axis results in some strange happenings. I guess there is some problem with the quanternion calculations but require some help here. (I'm still working on my 3D maths).

Attached is what I have. cs code

Thanks for your help. Once working I hope others will find the code useful too :)