make cover page background darker

Author: sarabander

index.xhtml

@@ -20,6 +20,7 @@ http://coding.smashingmagazine.com/2013/08/09/absolute-horizontal-vertical-cente
 http://coding.smashingmagazine.com/2013/05/22/centering-elements-with-flexbox/
 */
 body {
+  background-color: #f0f0f0;
   display: -webkit-box;
   display: -moz-box;
   display: -ms-flexbox;