Translation - spanish

Translation to Spanish, I named the file as 'es-GT.md' (like Spanish Guatemalan), but the translation is neutral, so it can be renamed to es.md to avoid confusion.

The translated chapters are:
- Single Responsibility
- IIFE
- Modules
- AngularJS Docs
- Contributing
- License

But if you prefer we can wait until the full translation is ready :).

Thanks for the guide, it has been very helpful in my work.