fix(package): update autoprefixer to version 7.0.1

Closes #207

Author: greenkeeper[bot]

package.json

@@ -11,7 +11,7 @@
   },
   "license": "MIT",
   "dependencies": {
-    "autoprefixer": "~6.7.7",
+    "autoprefixer": "~7.0.1",
     "babel-preset-env": "~1.4.0",
     "browser-sync": "~2.18.8",
     "cssnano": "~3.10.0",