Update README.md

Added Microsoft Edge as supported browser.

README.md

@@ -56,6 +56,7 @@ Check out our [integration wiki](https://github.com/Semantic-Org/Semantic-UI/wik
 * IE 11+
 * Android 4.4+, Chrome for Android 44+
 * iOS Safari 7+
+* Microsoft Edge 12 & 13
 
 Although some components will work in IE9, [grids](http://semantic-ui.com/collections/grid.html) and other [flexbox](https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Flexible_boxes) components are not supported by IE9 and may not appear correctly.