Update Brazilian Portuguese translation

Although SSR's Translation web page [1] says pt_BR is complete, a lot of strings required attention of a translator. I followed instructions on updating with 'lupdate-qt4' and finished translation. I hope it fits well.

[1] http://www.maartenbaert.be/simplescreenrecorder/translations/

Signed-off-by: Rafael Ferreira <rafael.f.f1@gmail.com>