String.prototype.rgb2hex

@Description: Takes an rgb string and converts it to hex color rgb(255,255,255) -> #FFFFFF
@File: String/prototype/rgb2hex.js
@Author: Paul Visco
@Version: 1.01 12/20/07
@Param: Number asArray If set to 1 then it returns the values as an array
@Return: Array A hex color array ['FF', 'FF', 'FF']
@Example:

var myString = 'rgb(255,255,255)';

var newString = myString.rgb2hex();
//newString = '#FFFFFF'