Add a getHref method to look for the attribute

This allows the overlay trigger to be something other than an <a> tag

js/modules/overlay.js

@@ -5,8 +5,8 @@
  * license MIT
  */
 define(
-  ['underscore', 'modules/addEvent', 'modules/clazz', 'modules/addScript'],
-  function(_, addEvent, clazz, addScript) {
+  ['underscore', 'modules/addEvent', 'modules/clazz', 'modules/data-attrs', 'modules/addScript'],
+  function(_, addEvent, clazz, data, addScript) {
 
     window.onYouTubeIframeAPIReady = apiCallbackYoutube;
     addScript("youtube-api", "//www.youtube.com/iframe_api");
@@ -64,7 +64,7 @@ define(
       e.returnValue = false;
 
       closeOverlay(e, true);
-      var id = (a.href || a.getAttribute('href')).replace(/^.*#(.*)$/, '$1');
+      var id = getHref(a).replace(/^.*#(.*)$/, '$1');
       clazz.add(document.getElementById(id), 'overlay-visible');
       clazz.add(backdrop, 'backdrop-visible');
       addEvent(window, 'keyup', overlayKeypress);
@@ -85,7 +85,7 @@ define(
     }
 
     function initOverlay(a) {
-      var id = a.href.replace(/^.*#(.*)$/, '$1');
+      var id = getHref(a).replace(/^.*#(.*)$/, '$1');
       if (!id) { return; }
       var overlay = document.getElementById(id);
       document.body.appendChild(overlay);
@@ -94,6 +94,10 @@ define(
       addEvent(a, 'click', _.bind(triggerOverlay, this, a));
     }
 
+    function getHref(a) {
+      return a.href || a.getAttribute('href') || data.get(a, 'href');
+    }
+
     return {
       initAll: initAllOverlays,
       init: initOverlay