Changes in 2.5:
	- Added an optional native method for hash calculation for
	  additional speed improvement.
	- Cleaned up the code a little to make it friendlier to Javadoc.
Changes in 2.1:
	- Added a note to Update(String) explaining that the results of the
	  method may vary across platforms.  Thanks to Peter Speck for
	  pointing this out.
	- Added an overloaded version of the Update() method which takes
	  as parameters both a String and a character encoding for
	  converting the String to a byte array.
