Remove example, fix coding style issues

Author: afshinm

example/bad-opacity-example/index.html

@@ -636,8 +636,10 @@
     while (parentElm != null) {
       if (parentElm.tagName.toLowerCase() === 'body') break;
 
+      //fix The Stacking Contenxt problem. 
+      //More detail: https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Understanding_z_index/The_stacking_context
       var zIndex = _getPropValue(parentElm, 'z-index');
-	  var opacity = parseFloat(_getPropValue(parentElm, 'opacity'));
+      var opacity = parseFloat(_getPropValue(parentElm, 'opacity'));
       if (/[0-9]+/.test(zIndex) || opacity < 1) {
         parentElm.className += ' introjs-fixParent';
       }