Remove fixed navbar from docs

docs/_static/custom.css

@@ -8,7 +8,7 @@ html {
 body {
   /* Margin bottom by footer height */
   margin-bottom: 60px;
-  padding-top: 50px;
+  /*padding-top: 50px; */ /* uncomment if navbar should be fixed */
 }
 
 body,

docs/_templates/layout.html

@@ -18,7 +18,7 @@
 
 {# Nav should appear before content, not after #}
 {%- block content %}
-<nav class="navbar navbar-default navbar-fixed-top topnav" role="navigation">
+<nav class="navbar navbar-default navbar-top topnav" role="navigation">
     <div class="container topnav">
         <div class="navbar-header">
             <button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#topnav-collapse">