Trying to optimize a plane in Unity [closed]

Question

So unity provides gameobject creation of a plane which contains a lot of triangles Unity calculates which is really unneeded for a simple plane. I was following a tutorial on how to do this, but I am getting an error.

Optimized Plane script:

#pragma strict

class OptPlane extends Editor{
@MenuItem("GameObject/Create Other/Opt Plane")

static function Init (){
    var customPlane : GameObject = new GameObject("Optimized Plane");
    var meshFilter : MeshFilter  = customPlane.AddComponent(MeshFilter);
    customPlane.AddComponent(MeshRenderer);

    var destination : String = "Asset/Model/OptimizedPlane.asset";
    var mesh : Mesh = AssetDatabase.LoadAssetAtPath(destination, Mesh);

    if(! mesh){
        mesh      = Mesh();
        mesh.name = 'Optimized Plane';

        var vertices : Vector3[]  = [Vector3(-1,0,1), Vector3(1,0,1), Vector3(1,0,-1), Vector3(-1,0,-1)];
        var uv       : Vector2[]  = [Vector2(-1,1), Vector2(1,1), Vector2(1,-1), Vector2(-1,-1)];
        var tangents : Vector4[]  = [Vector4(-1,0,1,1), Vector4(1,0,1,1), Vector4(1,0,-1,1), Vector4(-1,0,-1,1)];
        var triangles: int[]      = [0,1,3,3,1,2];

        mesh.vertices  = vertices;
        mesh.uv        = uv;
        mesh.tangents  = tangents;
        mesh.triangles = triangles;

        mesh.RecalculateNormals();
        mesh.RecalculateBounds();
        mesh.Optimize();
        AssetDatabase.CreateAsset(mesh, destination);
        AssetDatabase.SaveAssets();
    }

    meshFilter.mesh = mesh;
    Selection.activeObject = customPlane;
}

Warning: UnityException: Creating asset at path Asset/Model/OptimizedPlane.asset failed. OptPlane.Init () (at Assets/Editor/OptPlane.js:32)

I understand that it can't create it to this location I sent it, but from the tutorial he did nothing special besides create a "Model" folder and it just worked for him. Also, what is this .asset extension? I am just guessing it is what Unity uses to create objects in the scene or something.

Here is the link for reference. http://www.youtube.com/watch?feature=player_detailpage&v=ojEAHx_vY3U#t=1952s