chore(package): update url-loader to version 4.0.0

Closes #342

Author: greenkeeper[bot]

package.json

@@ -83,7 +83,7 @@
     "sinon-chai": "^2.9.0",
     "source-map-loader": "^0.2.1",
     "style-loader": "^0.21.0",
-    "url-loader": "^1.0.0",
+    "url-loader": "^4.0.0",
     "webpack": "^3.0.0",
     "webpack-dev-server": "^2.4.4"
   },