Major testing

v1 works with anchor tags. Because of this feature, it clearly separates
behaviour from design. However it can only have 1 level of tabbing.

v2 works with paired objects ({tab: , block: }), within an array. This
turned out to be a bad idea as the logic of the arrays (and their
structure) wasn't reflected in the DOM. I'm keeping this code only for
the heck of it...

v3 very versatile, can handle many levels of tabbing, better separation
of concern. Each tab/section is paired via a data-attribute.