chore(package): update webpack to version 4.32.1

Closes #14

Author: greenkeeper[bot]

package.json

@@ -35,6 +35,6 @@
     "jsdom": "^11.1.0",
     "sinon": "^4.0.0",
     "mocha": "^4.0.0",
-    "webpack": "^3.0.0"
+    "webpack": "^4.32.1"
   }
 }