chore(package): update autoprefixer to version 7.0.0 (#589)

Author: greenkeeper[bot]

package.json

@@ -26,7 +26,7 @@
   },
   "devDependencies": {
     "ascii-table": "0.0.9",
-    "autoprefixer": "^6.7.2",
+    "autoprefixer": "^7.0.0",
     "babel-core": "^6.22.1",
     "babel-loader": "^7.0.0",
     "babel-plugin-transform-object-assign": "^6.8.0",