chore(package): update autoprefixer to version 9.6.0

Closes #331

Author: greenkeeper[bot]

package.json

@@ -41,7 +41,7 @@
     "@babel/core": "7.2.2",
     "@babel/plugin-syntax-object-rest-spread": "7.2.0",
     "@babel/preset-env": "7.3.1",
-    "autoprefixer": "9.4.7",
+    "autoprefixer": "9.6.0",
     "babel-loader": "8.0.5",
     "clean-webpack-plugin": "1.0.1",
     "concurrently": "4.1.0",