Apply contribution guidelines to "Validator" class
Apply contribution guidelines to "Validator" class

Also removes the possibility of the "create()" method to create a new
Validation with predefined rules since that is the behavior that the
constructor already has.

And even though may be a bit scary to make "Validator" final I believe
there should be no reason for this class to be extended, and if there is
it is probably because we are missing something, which I would very much
like to find out.

Signed-off-by: Henrique Moody <3be1622bc44cadc0ae4da5043bd847b230c854e8@gmail.com>

Respect/Validation,Respect/Validation