chore(package): update postcss-loader to version 2.0.5

Closes #346

package.json

@@ -46,8 +46,8 @@
     "minilog": "3.1.0",
     "mkdirp": "^0.5.1",
     "postcss-import": "9.1.0",
-    "postcss-loader": "1.3.3",
-    "postcss-simple-vars": "4.0.0",
+    "postcss-loader": "^2.0.5",
+    "postcss-simple-vars": "^4.0.0",
     "prop-types": "15.5.8",
     "react": "15.5.4",
     "react-dom": "15.5.4",