Changes

I found [http://www.mutationevent.com/projects/validate.js/index.php this code] can be useful for my Java assignment. Good thing is we can use the third party code now (properly cited!).

However it's missed a few features. So I've added those and sent the diff to [http://www.mutationevent.com/projects/validate.js/suggestions.php the author]:

1. regexp validation

2. rule can be optional - validate only if not empty