chore(package): update postcss-loader to version 2.0.3

Closes #87

Author: greenkeeper[bot]

package.json

@@ -92,7 +92,7 @@
     "npm-run-all": "^4.0.0",
     "optimize-js-plugin": "0.0.4",
     "parse5": "^3.0.1",
-    "postcss-loader": "^1.0.0",
+    "postcss-loader": "^2.0.3",
     "raw-loader": "0.5.1",
     "resolve-url-loader": "^1.4.3",
     "rimraf": "~2.5.4",