Usar strings puras ao invés de structs (williamgueiros#39)

Merge pull request williamgueiros#32 from williamgueiros/remove-basic…

…-validation

Remove validação de numeros básicos

Merge pull request williamgueiros#31 from williamgueiros/validate_gen…

…erated

Garantir a validade de cnpjs gerados

Merge pull request williamgueiros#30 from williamgueiros/special-cnpj

Casos especiais de cnpj

Consertar specs (williamgueiros#25)