Make it possible to switch all tabs on a page

[drewhk]

As a Java developer, I would find it very annoying to flip all tabs one-by-one to Java for example.

[eed3si9n]

+1

[pvlugter]

Yes, we've wanted to add this too. Even better if it remembered a preference for the whole documentation site.

In the cinnamon documentation, we've also used tabs in a different way (from build tool or programming language) where we have the minimal configuration in the main tab and the possible defaults from the reference.conf in a secondary tab. We've found this to be useful. And in this case, we don't want to switch all tabs on a page or remember a preference. Examples on this page:

http://monitoring.lightbend.com/docs/2.0.x/plugins/chmetrics/reporters.html

So if this feature could have switching all tabs by default, but possible to turn off for something like the configuration tabs.

[ktoso]

+1 once more, this is very important for us, both Akka and Akka HTTP need this a lot,
esp. if we are to move to more consolidated docs.

Relates to: akka/akka-http#527

[pvlugter]

Fixed in #107.