docs: Update fonts to be loaded over SSL (#44)

Author: colelawrence

_includes/head.html

@@ -10,5 +10,5 @@
 
     <link rel="icon" href="{{"/assets/img/favicon.ico"|prepend:site.baseurl}}">
     <link rel="stylesheet" href="{{"/assets/css/index.css"|prepend:site.baseurl}}">
-    <link rel="stylesheet" href="http://fonts.googleapis.com/css?family=Open+Sans:400,700,800,600">
+    <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Open+Sans:400,700,800,600">
 </head>