Update the html-webpack-plugin dependency to the latest beta version

Author: DominikPalo

package.json

@@ -33,7 +33,7 @@
     "cheerio": "^0.22.0",
     "css-loader": "^0.25.0",
     "extract-text-webpack-plugin": "^1.0.1",
-    "html-webpack-plugin": "^2.16.0",
+    "html-webpack-plugin": "^4.0.0-beta.4",
     "jasmine": "^2.4.1",
     "rimraf": "^2.5.2",
     "semistandard": "^7.0.5",