Fix slidenav-trigger target

app/templates/header.html.j2

 <header>
   <nav>
     <ul class="left hide-on-large-only">
-      <li><a href="#" data-target="sidenav" class="sidenav-trigger"><i class="material-icons">menu</i></a></li>
+      <li><a href="#" data-target="slide-out" class="sidenav-trigger"><i class="material-icons">menu</i></a></li>
     </ul>
     <div class="nav-wrapper">
       <span class="brand-logo center">