React component to expand at most one contained card.
<Wizard show={[
this.state.expand_first,
this.state.expand_second
]}>
<div id="first_expanded">
…
</div>
<div id="first_collapsed">
…
</div>
<div id="second_expanded">
…
</div>
<div id="second_collapsed">
…
</div>
</Wizard>