AngularJS port

I haven’t ported the IE6 & IE7 fixes, as AngularJS does not support these browsers.

For IE8, I’ve followed the AngularJS 1.3 approach: it should work, but has not been tested in this browser.

The placeholder and autofocus polyfills have been tested in IE9.

[AngularJS Internet Explorer Compatibility](https://docs.angularjs.org/guide/ie)