adding sandbox support to the iframe for chrome apache-less support

Author: dmolsen

source/_patternlab-files/index.mustache

@@ -23,7 +23,7 @@
 		<div id="sg-vp-wrap">
 			<div id="sg-cover"></div>
 			<div id="sg-gen-container">
-				<iframe id="sg-viewport"></iframe>
+				<iframe id="sg-viewport" sandbox="allow-same-origin allow-scripts"></iframe>
 				<div id="sg-rightpull-container">
 					<div id="sg-rightpull"></div>
 				</div>