o) 21 Aug 2001
    - initial release

o) 22 Aug 2001
    - now when a class name is passed it checks via

           if ((blessed( $class ) || string( $class )) && $class->isa( $shouldbe )) {

      so that you can call it as a class method and still pass the signature.

o) 30 Oct 2001
    - Patches by Leon Brocard:
    - new test suite (100 tests!) to expose bugs
    - renamed int to integer so that it now works
    - string now works
    - number now works
    - can now set and check returned values using 'returns'
    (note associated change in getSignature)