translate from english to spanish

I've translated 'introduccion-a-rails/permitir_votar' to spanish.

Preserved original example code without changes.
I put the 'Deploy To Heroku' link's text as 'Colocar En Linea Con
Heroku', since 'deploy' has no intuitive translation to spanish to my
knowledge.

Hope I won that free pass to Magma. I'm such a fan ;P