add Pod encoding marker

Hi,

The lack of encoding marker causes mojibakes in place of non-ASCII symbols on [sco](http://search.cpan.org/~hernan/WWW-Tabela-Fipe-0.002/lib/WWW/Tabela/Fipe.pm): `Ã© sÃ³ executar`.

[MetaCPAN](https://metacpan.org/pod/WWW::Tabela::Fipe) gets it right, but warns at the bottom of the page.

Explicit encoding marker should fix both of those.

Cheers,
Sergey