don't convert anchors with child nodes to rolling links (closes #266)

js/reveal.js

@@ -527,7 +527,7 @@ var Reveal = (function(){
 			for( var i = 0, len = nodes.length; i < len; i++ ) {
 				var node = nodes[i];
 
-				if( node.textContent && !node.querySelector( 'img' ) && ( !node.className || !node.classList.contains( node, 'roll' ) ) ) {
+				if( node.textContent && !node.querySelector( '*' ) && ( !node.className || !node.classList.contains( node, 'roll' ) ) ) {
 					var span = document.createElement('span');
 					span.setAttribute('data-title', node.text);
 					span.innerHTML = node.innerHTML;