chore(package): update postcss-loader to version 2.1.5

Author: greenkeeper[bot]

package.json

@@ -33,7 +33,7 @@
     "file-loader": "1.1.11",
     "mini-css-extract-plugin": "0.4.0",
     "node-sass": "4.9.0",
-    "postcss-loader": "2.1.4",
+    "postcss-loader": "2.1.5",
     "sass-loader": "7.0.1",
     "stylelint": "9.2.0",
     "stylelint-order": "0.8.1",