function syncSlide( slide = currentSlide ) {

		backgrounds.sync( slide );
		fragments.sync( slide );

		slideContent.load( slide );

		backgrounds.update();
		notes.update();

	}
Updates reveal.js to keep in sync with new slide attributes. For
example, if you add a new `data-background-image` you can call
this to have reveal.js render the new background image.

Similar to #sync() but more efficient when you only need to
refresh a specific slide.

@param {HTMLElement} slide