Type Attributes List support

Hi,

Here is a part of my API blueprint "code":

```
+ Response 200 (application/json)
+ Attributes (boolean, sample:false)
```

I use Type Definition, according to this doc: https://github.com/apiaryio/mson/blob/master/MSON%20Specification.md#35-type-definition .

However, when generated it looks like this in aglio-generated html.

I think it should put `false` there.

Am I right?

Regards,

No source file or test is named. Reproduce the issue with the supplied API Blueprint and inspect the generated HTML to trace how the boolean Type Definition is rendered; done means the generated output displays the sample value false.

Written by the indexing model from the issue text.