This way we simplify the HTML and generating similar menus will be
easier. We also improve the experience for screen reader users, who
might have been hearing the icons as text because we weren't using the
`aria-hidden` attribute.
We're still keeping the "icon-" classes for compatibility with CONSUL
installations which might have changed this code.
From a semantic point of view, there's no reason to add a strong
emphasis to the menu items.
Besides, using CSS simplifies the code and is less error-prone. For
instance, the "stats" section didn't have a <strong> tag, and so it was
the only one which wasn't bold.
Now that there's no naming confict with the helper method used in the
ProposalsDashboardHelper, we can easily simplify the view, moving the
logic to the Ruby class.
The HTML `class` attribute was declared twice and so the second one was
being ignored.
In the case of messages, it was "working" properly because the
`class=is-active` part is not used on `<li>` tags when they've got a
`<ul>` inside them.
We no longer need to use the `menu_` prefix, since now these methods
aren't helper methods anymore, and so their names won't collide with
other helpers.
