I18n + brazilian portuguese support

Saluton,

I think it closes the issue #7. The only part I couldn't internationalize was the date selector, when post is being created or edited. Let me explain why:

- Pikaday isn't 100% ready/friendly for i18n;

- I've tried to give another date pattern instead of "YYYY-MM-DD", but unfortunately this kind of pattern differs from the rails date patterns, eg: `%Y-%m-%d`.