Use protocol-relative URL in example

getting-started.html

@@ -104,7 +104,7 @@ bootstrap/
     <h1>Hello, world!</h1>
 
     <!-- jQuery (necessary for Bootstrap's JavaScript plugins) -->
-    <script src="http://code.jquery.com/jquery.js"></script>
+    <script src="//code.jquery.com/jquery.js"></script>
     <!-- Include all compiled plugins (below), or include individual files as needed -->
     <script src="js/bootstrap.min.js"></script>