Navbar Updates

- Navigation is no longer fixed to the top of the window
- Lens navigation only appears when there are actually items to display

analytics_dashboard/static/sass/_base.scss

@@ -55,6 +55,11 @@ hr.has-emphasis {
 
 // nav + header
 // --------------------
+.navbar {
+  margin-bottom: 0;     // Get rid of Bootstrap's default margin. Many of our pages have a secondary navbar
+                        // that needs to sit right below the main navbar.
+}
+
 .navbar-brand {
   padding: 25px 50px;    // needed for edX logo to render properly
 
@@ -308,8 +313,6 @@ hr.has-emphasis {
 // view: dashboard
 // --------------------
 .view-dashboard {
-  padding-top: $navbar-height;                                                                      // move down content because we have a fixed navbar
-
   .main {
     padding: ($padding-large-vertical*2) ($padding-large-horizontal*3);
   }

analytics_dashboard/templates/header.html

@@ -4,7 +4,7 @@
 Partial: App-wide header element
 {% endcomment %}
 
-<nav class="navbar navbar-default navbar-fixed-top" role="navigation" id="nav">
+<nav class="navbar navbar-default" role="navigation" id="nav">
   <div class="container">
     <div class="navbar-header">
       <button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#main-nav">

analytics_dashboard/templates/lens-navigation.html

@@ -2,6 +2,7 @@
 Partial for displaying the lens navigation and the sections within the lenses.
 {% endcomment %}
 
+{% if primary_nav_items %}
 <nav class="navbar navbar-default lens-nav" role="navigation">
     <div class="container ">
         <ul class="nav navbar-nav">
@@ -34,3 +35,4 @@ Partial for displaying the lens navigation and the sections within the lenses.
         </ul>
     </div>
 </nav>
+{% endif %}