chore(package): update css-loader to version 3.1.0

Closes #57

Author: greenkeeper[bot]

package.json

@@ -15,7 +15,7 @@
     "angularjs-testbed": "^0.3.3",
     "copyfiles": "2.1.0",
     "cross-env": "5.2.0",
-    "css-loader": "2.1.1",
+    "css-loader": "3.1.0",
     "file-loader": "3.0.1",
     "fork-ts-checker-webpack-plugin": "^1.3.3",
     "html-loader": "0.5.5",