showNavigation=false should remove the footer buttons rather than just hiding them

[agurczuk]

When the flag for ShowNavigation is set to false what results in the output is a

<div style="display: none" class='footer-buttons'> ... </div>

What should happen is the whole block should be removed from the DOM i.e.

this.props.showNavigation && <div className='footer-buttons>...</div>

Use case:
With the current approach the buttons are in the DOM. In my case when I nest the StepZilla inside a ReactModal the hidden elements confuse focus trapping, when tabbing Modal tries to tab into hidden element, gets most likely confused and tabs to the background. As a workaround I need to manually remove the 'footer-buttons' from the DOM which is not something I should need to do.

If there is a reason for the elements to be hidden instead of not rendered additional option would be nice.