fix(package): update autoprefixer to version 7.1.2

Closes #79

Author: greenkeeper[bot]

package.json

@@ -17,7 +17,7 @@
   },
   "dependencies": {
     "async": "^2.1.2",
-    "autoprefixer": "^6.5.1",
+    "autoprefixer": "^7.1.2",
     "babel-core": "^6.18.2",
     "babel-loader": "^6.2.7",
     "babel-polyfill": "^6.13.0",