To migrate from 3.x to 4.x, there are some changes that need to happen to your layout file.
Because of the way the titles work, the general layout has changed slightly.
<html>
<body>
<div class="body">
<nav class="navbar navbar-default">
...
</nav>
<div class="main-content" role="main">
<div class="container-fluid title-bar">
<ol class="breadcrumb">
<li>
<a href="/">Home</a>
</li>
</ol>
</div>
<div class="container"> <!-- or container fluid -->
content goes here
</div>
<footer role="main">
...
</footer>
</div>
</div>
</body>
</div>
The breadcrumbs now play a more important role in the layout now. They act as the title of the page. Typically you will want to keep these a bit short.
<ol class="breadcrumb">
<li>
<a href="/">Home</a>
</li>
<li class="active">
Current page
</li>
</ol>