Replaced Mesh.Optimize with MeshUtility.Optimize
Replaced Mesh.Optimize with MeshUtility.Optimize

Since Unity 5.6 [Mesh.Optimize() no longer exists](https://docs.unity3d.com/ScriptReference/Mesh.Optimize.html). It has been replaced by [MeshUtility.Optimize(mesh)](https://docs.unity3d.com/ScriptReference/MeshUtility.Optimize.html).
pharan/Unity-MeshSaver