Update for change for embed iframe link from quizlet

Quizlet may have changed their iframe embed link as this is an example embed link from their site.
<iframe src="http://quizlet.com/1518465/familiarize/embedv2/" height="410" width="100%" style="border:0;"></iframe>
Propose change here to fix iframe link in Canvas.
Merge pull request #4 from klloyd/patch-2

Update for change for embed iframe link from quizlet