Adds blog functionality with markdown files

This is a very simple and elegant implementation. I used the **postmarkdown** gem which allows you to create a very basic blog based on markdown files (like jekyll's functionality).

Also, I changed the permalinks in order to have a more RESTful pattern, and now they are ```http://domain.com/workshops/one```

### Planned for next commits

1. Hack the view **layout** in order to be like an event page
2. Add some actual **content** for the first event
3. Add some **disqus** comment system

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**Don't merge just yet!**