gistfile1.js

/*
I used your style, your header div, but with a slide like this

				<section data-state="showHeader" data-header="custom head">
				<p>Hello</p>
				</section>

*/

Reveal.addEventListener( 'slidechanged', function( event ) {
    // event.previousSlide, event.currentSlide, event.indexh, event.indexv
    if(event.currentSlide.dataset.header) {
    	myHead.innerHTML = event.currentSlide.dataset.header;
	}
} );