fixed issue with Body.applyForce torque, closes #64

Author: liabru

src/body/Body.js

@@ -581,7 +581,7 @@ var Axes = require('../geometry/Axes');
         body.force.x += force.x;
         body.force.y += force.y;
         var offset = { x: position.x - body.position.x, y: position.y - body.position.y };
-        body.torque += (offset.x * force.y - offset.y * force.x) * body.inverseInertia;
+        body.torque += offset.x * force.y - offset.y * force.x;
     };
 
     /**