Fix debug build to address issue #10

Travis fails to build on gcc due to wrapping.  Creating PR in the meantime since issue is unrelated to this fix.
Having  mass properties for ground just seems weird to me. I also don't agree that the mass properties of anything welded  to ground doesn't matter. They do matter if you are going to determine what the joint reaction force is say between the body and ground, right? I also have little sympathy for someone who defines a body with invalid mass properties and then decides to weld it to ground, so I don't think they should be spared warnings (exceptions) about invalid mass props. Having numbers associated with ground and simply ignoring them seems like evidence that ground isn't like every other body.  Since Body is soon to be a Frame .. maybe we could have a separate Ground (Frame). You can hang whatever you like on it just like any other Frame it just isn't a Body. Would that work?