chore(package): update postcss-loader to version 1.3.1

Closes #82

https://greenkeeper.io/

package.json

@@ -49,7 +49,7 @@
     "lodash.pick": "4.4.0",
     "minilog": "3.1.0",
     "opt-cli": "1.5.1",
-    "postcss-loader": "1.2.2",
+    "postcss-loader": "1.3.1",
     "postcss-modules-values": "1.2.2",
     "react": "15.4.2",
     "react-dom": "15.4.2",