chore(package): update css-loader to version 3.4.0

Closes #172

Author: greenkeeper[bot]

package.json

@@ -14,7 +14,7 @@
     "babel-core": "6.26.0",
     "babel-loader": "8.0.4",
     "babel-preset-es2015": "6.24.1",
-    "css-loader": "3.3.1",
+    "css-loader": "3.4.0",
     "extract-loader": "2.0.1",
     "file-loader": "4.0.0",
     "node-sass": "4.9.4",