Fix preview protocol when running under https
If the preview is served from behind an https proxy, then browsers will complain
about the content being mixed-mode and not load the `modestmaps-js` script.
By removing protocol from the `<script>` tag, the protocol of the current page
will be used by the browser.
@@ -742,7 +742,7 @@ def _preview(layer):
<html>
<head>
<title>TileStache Preview: %(layername)s</title>
- <script src="http://cdn.rawgit.com/stamen/modestmaps-js/v1.0.0-beta1/modestmaps.min.js" type="text/javascript"></script>
+ <script src="//cdn.rawgit.com/stamen/modestmaps-js/v1.0.0-beta1/modestmaps.min.js" type="text/javascript"></script>
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0">
<style type="text/css">
html, body, #map {
