Switch to https for the google fonts api

Author: fsalvi

_includes/headertop.html

@@ -17,7 +17,7 @@
     <!-- Bootstrap CSS -->
     <link rel="stylesheet" href="{{ site.baseurl }}/resources/css/bootstrap.css" type="text/css" />
 
-    <link href='http://fonts.googleapis.com/css?family=Source+Sans+Pro:400,600,700,900,400italic,700italic' rel='stylesheet' type='text/css'>
+    <link href='https://fonts.googleapis.com/css?family=Source+Sans+Pro:400,600,700,900,400italic,700italic' rel='stylesheet' type='text/css'>
 
     <!-- Custom stylesheet -->
     <link rel="stylesheet" href="{{ site.baseurl }}/resources/css/main.css" type="text/css" />