Update to webpack 4

- Remove unused base64-loader

package.json

@@ -26,12 +26,11 @@
   "devDependencies": {
     "babel-core": "^6.23.1",
     "babel-eslint": "^8.2.1",
-    "babel-loader": "^7.1.2",
+    "babel-loader": "^7.1.4",
     "babel-polyfill": "^6.22.0",
     "babel-preset-es2015": "^6.22.0",
-    "base64-loader": "^1.0.0",
     "chromeless": "^1.5.1",
-    "copy-webpack-plugin": "^4.0.1",
+    "copy-webpack-plugin": "^4.5.1",
     "docdash": "^0.4.0",
     "eslint": "^4.6.1",
     "eslint-config-scratch": "^5.0.0",
@@ -49,8 +48,10 @@
     "tap": "^11.0.0",
     "travis-after-all": "^1.4.4",
     "twgl.js": "4.4.0",
-    "webpack": "^3.10.0",
-    "webpack-dev-server": "^2.8.2",
+    "uglifyjs-webpack-plugin": "^1.2.5",
+    "webpack": "^4.8.0",
+    "webpack-cli": "^2.0.15",
+    "webpack-dev-server": "^3.1.4",
     "xml-escape": "1.1.0"
   }
 }