cb = function(){
            clearTimeout( to );
            if ( call ){
                call = false;
                to = setTimeout(cb, delay);
                fn.apply(scope, args);
            } else {
                to = false;
            }
        }
Physics.util.throttle( fn, delay ) -> Function
- fn (Function): The function to throttle
- delay (Number): Time in milliseconds

Ensure a function is only called once every specified time span.