Edit autoprefixer browser options (#721)

New browser options provide wider support for browsers.

Author: lukasmatta

gulpfile.js

@@ -24,7 +24,7 @@ var opts = {
   concatName: 'animate.css',
 
   autoprefixer: {
-    browsers: ['last 2 versions'],
+    browsers: ['> 1%, last 2 versions, Firefox ESR'],
     cascade: false
   },