chore(package): update autoprefixer to version 9.0.0 (#5624)

package.json

@@ -217,7 +217,7 @@
     "webpack-isomorphic-tools": "3.0.6"
   },
   "devDependencies": {
-    "autoprefixer": "^8.0.0",
+    "autoprefixer": "^9.0.0",
     "babel-core": "^6.24.1",
     "babel-eslint": "^8.2.1",
     "babel-gettext-extractor": "git+https://github.com/muffinresearch/babel-gettext-extractor.git#0d39d3882bc846e7dcb6c9ff6463896c96920ce6",