fix(package): update postcss-loader to version 2.1.6

Closes #33

Author: greenkeeper[bot]

package.json

@@ -44,7 +44,7 @@
     "marked": "0.3.6",
     "minimist": "1.2.0",
     "postcss-advanced-variables": "1.2.2",
-    "postcss-loader": "1.1.0",
+    "postcss-loader": "2.1.6",
     "prettyjson": "1.1.3",
     "react": "^15.3.2",
     "react-codemirror": "0.2.6",