added safer filter for open.location in run.js

@@ -12,7 +12,10 @@ var casper = require('casper').create({
 
 // Overriding Casper.open to prefix all test urls
 casper.setFilter('open.location', function(location) {
-    return 'file://' + phantom.casperPath + '/' + location;
+    if (!/^http/.test(location)) {
+        return 'file://' + phantom.casperPath + '/' + location;
+    }
+    return location;
 });
 
 var tests = [];