Edit: Possibly a better option for all browsers.
<script src="//cdn.polyfill.io/v2/polyfill.min.js?features=es5,es6,es7,Promise,fetch,html5-elements,viewport&flags=gated"></script>
Below are the shims I'm currently using for a React app in conjunction with Bootstrap (react-bootstrap)
<!--[if lt IE 9]>
<script>
(function(){
var ef = function(){};
window.console = window.console || {log:ef,warn:ef,error:ef,dir:ef};
}());
</script>
<script src="//cdnjs.cloudflare.com/ajax/libs/html5shiv/3.7.2/html5shiv.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/html5shiv/3.7.2/html5shiv-printshiv.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/1.11.1/jquery.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/es5-shim/3.4.0/es5-shim.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/es5-shim/3.4.0/es5-sham.js"></script>
<![endif]-->