Afrikaans locale translation

Hi Sven!

I met Reneé de Voursney yesterday at the Railsbridge. We discussed an Afrikaans translation, and here it is! 

I'm a complete novice to RoR, so please let me know if there's anything that needs to change. I ran the rake spec, and got 0 errors.

It would be great if you would consider this pull request?

Best regards
Suné