I've fixed some minor errors and revised some texts in order to provide better sense for the text.
Beside that, I've reduced the text (keeping it's meaning of course) of the buttons close to the bottom of the front page, since on Firefox, Chrome and Safari, the buttons seems to not be adaptive oriented as the main text divs.
Added header with contributor name and contact for future inquires regarding pt-br translation.
Legal stuff, bottom and header translated, links comments translated whenever possible.
Please inform me if new translating keys get's added, so I can maintain this translation updated.
Translation done with love from Brazil.
gustavohmsilva