Add crossorigin attribute to script tags

Helps when tests are loading files from another localhost server.

Addresses an issue where errors from scripts loaded from another server would read as "Script Error" without any additional information on to where the error was produced.

This articles contains details on the "Script Error" case: https://blog.getsentry.com/2016/05/17/what-is-script-error.html

lib/middleware/karma.js

@@ -27,7 +27,7 @@ var urlparse = function (urlStr) {
 var common = require('./common')
 
 var VERSION = require('../constants').VERSION
-var SCRIPT_TAG = '<script type="%s" src="%s"></script>'
+var SCRIPT_TAG = '<script type="%s" src="%s" crossorigin="anonymous"></script>'
 var LINK_TAG_CSS = '<link type="text/css" href="%s" rel="stylesheet">'
 var LINK_TAG_HTML = '<link href="%s" rel="import">'
 var SCRIPT_TYPE = {