Added RG validation

[raphaklaus]

#7

[the-darc]

The created method says that my RG is not valid (my RG is 11862763).

Note: I don't know if there is a way to validate RG. See: http://pt.stackoverflow.com/questions/71/valida%C3%A7%C3%A3o-de-rg

[raphaklaus]

This validations aims General Registry which contains 9 digits.