Added vendor prefixes

gatsby-node.js

@@ -1,11 +1,15 @@
 var rucksack = require('rucksack-css')
+var autoprefixer = require('autoprefixer')
 var lost = require("lost")
 
 exports.modifyWebpackConfig = function(config, env) {
     config.merge({
         postcss: [
             lost(),
-            rucksack()
+            rucksack(),
+            autoprefixer({
+                browsers: ['>1%', 'ie >= 10', 'safari >= 6', 'last 3 versions']
+            })
         ]
     })