Install
	yum install firefox
	yum install xvfb
	gem install bundler
	bundle install
	
First, We need a browser, in this project, I chose Firefox, you could use any you want except text mode browser such as lynx. Then, I simulated the user action in the browser via watir-webdriver. Especially, if your machince didn't have GUI window, you have to run this script in headless mode(http://en.wikipedia.org/wiki/Xvfb).

Run
	/usr/bin/ruby AWSInvoiceDownloader.rb
	The latest invoice.pdf would be located in the directory of invoices.
	Enjoy it !