Add to_param for friendlier url's

You just need to add the to_param to the class where you want the nice url to be present, in this case de Artcile model.

```ruby
def to_param
    "#{id}-#{name}".parameterize
end
```

Also a gotcha here is on the link_to helper method you have to add the object in order to get the expected result such as:

```ruby
link_to article.title, article_path(article)
```