Add test for HTML Imports

* Test page: http://jsbin.com/lineheco/1

   AFAIK, this feature is only available in Chrome with the appropriate flag enabled:

   ![](https://f.cloud.github.com/assets/1223565/2241141/7575772c-9cc2-11e3-95bd-dcf28616d446.png)
 
* Useful links:
  * [W3C HTML Imports Specification](http://w3c.github.io/webcomponents/spec/imports/)
  * [HTML5Rocks: HTML Imports](http://www.html5rocks.com/en/tutorials/webcomponents/imports/)

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Let me know if I need to make any other changes.