fix(cards): imagesUrl when module is loaded asychronously

Author: richardschneider

README.md

@@ -21,18 +21,12 @@ Install with [npm](http://blog.npmjs.org/post/85484771375/how-to-install-npm)
 
 ### Browser
 
-Include the package from your project
-
-````html
-<link rel="stylesheet" type="text/css" href="./node_modules/cardsJS/dist/cards.min.css" />
-<script src="./node_modules/cardsJS/dist/cards.min.js" type="text/javascript"></script>
-````
-
-or from the [unpkg CDN](https://unpkg.com)
+Include the package from the [unpkg CDN](https://unpkg.com)
 
 ````html
 <link rel="stylesheet" type="text/css" href="https://unpkg.com/cardsJS/dist/cards.min.css" />
-<script src="https://unpkg.com/cardsJS/dist/cards.min.js"  type="text/javascript"></script>
+
+<script src="https://unpkg.com/cardsJS/dist/cards.min.js" type="text/javascript"></script>
 ````
 
 ## Cards

cards.js

@@ -1,5 +1,7 @@
 /*jslint vars: true, plusplus: true, -W003 */
 /*globals window, document, define, exports, module, require */
+
+var cardsScript = document.currentScript;
 
 (function (root, factory) {
     'use strict';
@@ -302,9 +304,8 @@
     });
 
     // Default imagesUrl to a subfolder of the script source.
-    var mySource = document.currentScript.src;
-    if (mySource) {
-        var path = mySource.substring(0, mySource.lastIndexOf('/')) + '/cards/';
+    if (cardsScript && cardsScript.src) {
+        var path = cardsScript.src.substring(0, cardsScript.src.lastIndexOf('/')) + '/cards/';
         module.options.imagesUrl = path;
     }