How do I change Bootstrap 3 column order on mobile layout?

I'm making a responsive layout with a top fixed navbar. Underneath I have two columns, one for a sidebar (3), and one for content (9). Which on desktop looks like this

navbar
[3][9]

When I resize to mobile the navbar is compressed and hidden, then the sidebar is stacked on top of the content, like this:

navbar
[3]
[9]

I would like the main content at the top, so I need to change the order on mobile to this:

navbar
[9]
[3]

I found this article which covers the same points, but the accepted answer has been edited to say that the solution no applies to the current version of Bootstrap.

How can I reorder these columns on mobile? Or alternatively, how can I get the sidbar list-group into my expanding navbar?

Here is my code:

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<!-- Latest compiled and minified CSS -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">

<!-- Optional theme -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap-theme.min.css" integrity="sha384-rHyoN1iRsVXV4nD0JutlnGaslCJuC7uwjduW9SVrLvRYooPp2bWYgmgJQIXwl/Sp" crossorigin="anonymous">

<!-- Latest compiled and minified JavaScript -->
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>

<div class="navbar navbar-inverse navbar-static-top">
  <div class="container">
    <a href="#" class="navbar-brand">Brand Title</a>
    <button class="navbar-toggle" data-toggle="collapse" data-target=".navHeaderCollapse">
      <span class="icon-bar"></span>
      <span class="icon-bar"></span>
      <span class="icon-bar"></span>
    </button>
    <div class="collapse navbar-collapse navHeaderCollapse">

    <ul class="nav navbar-nav navbar-right"><!--original navbar-->
      <li class="active"><a href="#">Home</a></li>
      <li><a href="#">FAQ</a></li>
    </ul>

    </div>
  </div>
</div><!--End Navbar Div-->
    <div class="container">
  <div class="row">

    <div class="col-lg-3">
  <div class="list-group">
    <a href="#" class="list-group-item">
    <h4 class="list-group-item-heading">Lorem ipsum</h4>
    <p class="list-group-item-text">Lorem Ipsum is simply dummy text.</p></a>
  </div>
</div><!--end sidebar-->


<div class="col-lg-9">
  <div class="panel panel-default">
    <div class="panel-body">
      <div class="page-header">
     Main Content
    </div>
  </div>
</div><!--end main content area-->

You cannot change the order of columns in smaller screens but you can do that in large screens.

So change the order of your columns.

<!--Main Content-->
<div class="col-lg-9 col-lg-push-3">
</div>

<!--Sidebar-->
<div class="col-lg-3 col-lg-pull-9">
</div>

By default this displays the main content first.

So in mobile main content is displayed first.

By using col-lg-push and col-lg-pull we can reorder the columns in large screens and display sidebar on the left and main content on the right.

Working fiddle here.

Updated 2018

For the original question based on Bootstrap 3, the solution was to use push-pull.

In Bootstrap 4 it's now possible to change the order, even when the columns are full-width stacked vertically, thanks to Bootstrap 4 flexbox. OFC, the push pull method will still work, but now there are other ways to change column order in Bootstrap 4, making it possible to re-order full-width columns.

Method 1 - Use flex-column-reverse for xs screens:

<div class="row flex-column-reverse flex-md-row">
    <div class="col-md-3">
        sidebar
    </div>
    <div class="col-md-9">
        main
    </div>
</div>

Method 2 - Use order-first for xs screens:

<div class="row">
    <div class="col-md-3">
        sidebar
    </div>
    <div class="col-md-9 order-first order-md-last">
        main
    </div>
</div>

Bootstrap 4(alpha 6): http://www.codeply.com/go/bBMOsvtJhD
Bootstrap 4.1: https://www.codeply.com/go/e0v77yGtcr

Original 3.x Answer

For the original question based on Bootstrap 3, the solution was to use push-pull for the larger widths, and then the columns will show is their natural order on smaller (xs) widths. (A-B reverse to B-A).

<div class="container">
    <div class="row">
        <div class="col-md-9 col-md-push-3">
            main
        </div>
        <div class="col-md-3 col-md-pull-9">
            sidebar
        </div>
    </div>
</div>

Bootstrap 3: http://www.codeply.com/go/wgzJXs3gel

@emre stated, "You cannot change the order of columns in smaller screens but you can do that in large screens". However, this should be clarified to state: "You cannot change the order of full-width "stacked" columns.." in Bootstrap 3.