chore(package): update electron-webpack to version 2.8.1

Closes #29

Author: greenkeeper[bot]

package.json

@@ -39,7 +39,7 @@
     "electron": "1.7.11",
     "electron-builder": "^19.34.1",
     "electron-debug": "^1.1.0",
-    "electron-webpack": "1.9.0",
+    "electron-webpack": "2.8.1",
     "webpack": "^3.6.0",
     "webpack-dev-server": "^2.9.2",
     "xo": "^0.18.2"