update serif (change controls, fix links, change url)

The Serif theme was a little flaky previously

css/theme/serif.css

 /**
  * A simple theme for reveal.js presentations, similar
- * to the default theme. The accent color is darkblue.
+ * to the default theme. The accent color is brown.
  *
- * This theme is Copyright (C) 2012 Owen Versteeg, https://github.com/StereotypicalApps. It is MIT licensed.
- * reveal.js is Copyright (C) 2011-2012 Hakim El Hattab, http://hakim.se; so is the theme - beige.css - that this is based off of.
+ * This theme is Copyright (C) 2012-2013 Owen Versteeg, http://owenversteeg.com - it is MIT licensed.
  */
 /*********************************************
  * GLOBAL STYLES
@@ -48,6 +47,7 @@ body {
  * LINKS
  *********************************************/
 .reveal a:not(.image) {
+  line-height: 1.3em;
   color: #51483d;
   text-decoration: none;
   -webkit-transition: color .15s ease;
@@ -87,6 +87,9 @@ body {
 /*********************************************
  * NAVIGATION CONTROLS
  *********************************************/
+.reveal .controls div {
+  opacity: 0.15; }
+
 .reveal .controls div.navigate-left,
 .reveal .controls div.navigate-left.enabled {
   border-right-color: #51483d; }