Fixed navigation bug (issue #2)

scss/_global-settings.scss

+/// Override nav-threshold because we have a larger menu
+$navigation-threshold: 864px;

scss/_vanilla-theme.scss

@@ -17,6 +17,9 @@
     <http://www.gnu.org/licenses/>.
 */
 
+// Import custom settings
+@import 'global-settings';
+
 // Import custom modules
 @import 'modules/tweaks';
 @import 'modules/navbar';