use protocol-relative URL for Roboto font in app-android-notes example

docs/examples/app-android-notes/index.html

@@ -8,7 +8,7 @@
     <meta name="apple-mobile-web-app-status-bar-style" content="black">
 
     <!-- Roboto -->
-    <link rel="stylesheet" href="http://fonts.googleapis.com/css?family=Roboto:400,500,700">
+    <link rel="stylesheet" href="//fonts.googleapis.com/css?family=Roboto:400,500,700">
 
     <link rel="stylesheet" href="../../dist/css/ratchet.min.css">
     <link rel="stylesheet" href="../../dist/css/ratchet-theme-android.min.css">