Miniumum Explorer version set to 11.

gulpfile.js

@@ -45,7 +45,7 @@ options.sass = {
 options.autoprefixer = {
   browsers: [
     '> 1%',
-    'ie 10'
+    'ie 11'
   ]
 };
 

sass/init/_variables.scss

@@ -18,7 +18,7 @@
 // Possible keys: chrome, edge, firefox, ie, opera, safari, '*'
 $support-for: (
   // IE 9-11
-  ie:  9,
+  ie:  11,
   // The last 4 versions of all other browsers.
   '*': -4,
 );