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

Closes #38

Author: greenkeeper[bot]

package.json

@@ -30,7 +30,7 @@
     "babel-loader": "^7.1.2",
     "babel-preset-es2015": "^6.24.1",
     "clean-webpack-plugin": "^1.0.0",
-    "css-loader": "^0.28.5",
+    "css-loader": "^3.1.0",
     "extract-text-webpack-plugin": "^3.0.0",
     "node-sass": "^4.5.3",
     "postcss-loader": "^2.0.6",