Add graceful handling for getJS 404s

[theroux]

In our dev environment we're using boot getJS but if someone forgets to check in a JS file to Github, it knocks out everyone else's JS as well. Would be nice if 404s did not affect the loading of other scripts.

<script type="text/javascript"> Boot.getJS({ src: 'http://o.aolcdn.com/os/aol/beacon.min.js', defer: 'ready', callback: '' }); Boot.getJS({ src: '%SITE-se-CDNRootURL%/js/plugins/jquery.clingify.js%SITE-se-CDNCacheBuster%', defer: 'ready', callback: '' }); Boot.getJS({ src: '%SITE-se-CDNRootURL%/js/se-nav-header.js%SITE-se-CDNCacheBuster%', defer: 'load', callback: '' }); Boot.getJS({ src: '%SITE-se-CDNRootURL%/js/se-article-share.js%SITE-se-CDNCacheBuster%', defer: 'load', callback: '' }); Boot.getJS({ src: '%SITE-se-CDNRootURL%/js/se-river.js%SITE-se-CDNCacheBuster%', defer: 'ready', callback: '' }); </script>