(1) 23 Aug, 2010	
	Add an option "-num_threads" to allow uses to specify the number of
	threads useda
(2) 12 April, 2012
	GCC 4.6 can successfully compile it. 

(3) 3 July, 2012
	Add a new option "-o" (or "--outfile") to allow users to specify the output file name.
	By default, it will output to STDOUT