Add support for ARIA attributes in tags

As part of our work in Rails Girls Summer of Code we have added support for ARIA attributes in tag helpers, so the users can set the attributes in this way:

```ruby
<%= f.text_field :name, aria: { required: "true", hidden: "false" } %>
```

And this will generate:

```html
<input aria-hidden="false" aria-required="true" id="user_name" name="user[name]" type="text">
```

We used the implementation of the ``data`` attributes as base for this.
Good idea. I'll push it.