How to Create a Tab UI with Riot 2.0

Aside from the usual unpleasantness of muddling together views and logic (and welcome back `onclick`, how I've missed you...), I find the idea of the "parent" scope rather troubling. If you have something nested inside a tab, let's say a link, what is its parent - an individual tab, or the whole "tabs" component?

Instead of

   class={ tabItem: true, is_active: something() }

you can just write

   class="tabItem { is_active: something() }"

Custom elements must contain a hyphen: http://w3c.github.io/webcomponents/spec/custom/#dfn-custom-e.... Just `<tabs>` is not allowed.

Of course we'd still have posts in 2015 about how to make tabs.