Active

This component manages the step active settings.

`property` activeClass : `'active'`

A class name to set on the current step.

`property` nestedActiveClass : `'nested-active'`

A class name to set on all parents of the current step.

`callback` setActive : `function( element, eventData )`

When a step is activated or selected.

`callback` setInactive : `function( element, eventData )`

When a previously active step is de-activated or not