String.prototype.numpad

@Description: Pads all numbers under 9 with a zero on the left
@File: String/prototype/numpad.js
@Author: Paul Visco
@Version: 1.0 11/19/07
@Return: String The original number padded to left with zero
@Example:

var myString = 9;

var newString = myString.numpad();
//newString = '09'