Use modelViewTransform instead of metersToPixels function

[aaronsamuel137]

During code review #56, we noticed two different kinds of transforms:

    // model coordinates are the same as view coordinates
    var modelViewTransform = ModelViewTransform2.createIdentity();

And

    // 1 meter is equal to 175 pixels
    metersToPixels: new LinearFunction( 0, 1, 0, 175 ),

It looks like the model coordinates should be in meters and the view coordinates are in "pixels". It would make more sense here to have a model view transform that goes from meters to pixels instead of passing around a function "metersToPixels". Can the metersToPixels function be removed and the modelViewTransform go from meters to screen coordinates?

[andrey-zelenkov]

Replace metersToPixels function by modelViewTransform. Reassign to @aaronsamuel137 for verification.

[aaronsamuel137]

Looks much better, thanks! Closing