Change username in navigation from static copy.

lms/templates/navigation.html

@@ -32,7 +32,7 @@
           <div class="divider"></div>
           <a href="${reverse('dashboard')}" class="user-link">
             <span class="avatar"><img src="${static.url('images/profile.jpg')}" /></span>
-            Neil deGrasse Tyson
+            ${user.username}
           </a>
           <div class="divider"></div>
           <a href="#" class="options">&#9662</a>