use protocol-relative URL to load libraries

browser will tell users that the page contains some insecure resources, use protocol-relative URL can prevent this issue.

reference : [The Protocol-relative URL](http://www.paulirish.com/2010/the-protocol-relative-url/)

index.html

@@ -10,7 +10,7 @@
 	<meta name="description" content="Sortable - is a minimalist JavaScript library for modern browsers and touch devices (No jQuery)."/>
 	<meta name="viewport" content="width=device-width, initial-scale=1"/>
 
-	<link href='http://fonts.googleapis.com/css?family=Roboto:300' rel='stylesheet' type='text/css'/>
+	<link href='//fonts.googleapis.com/css?family=Roboto:300' rel='stylesheet' type='text/css'/>
 
 	<style>
 		html {
@@ -288,7 +288,7 @@ sort.destroy();
 			<div style="margin-left: 30px">
 				<div><div class="layer title title_xl">See also</div></div>
 				<div id="rubaxa-repos" data-force="100" class="layer" style="margin-top: -8px; margin-left: 10px; width: 90%; background-color: #fff;">Loading&hellip;</div>
-				<script src="http://rubaxa.github.io/repos.js"></script>
+				<script src="//rubaxa.github.io/repos.js"></script>
 			</div>
 		</div>