chore(package): update uglifyjs-webpack-plugin, webpack-dev-server to latest

close #386 (false positive greenkeeper)
webpack-dev-server 3.1.11 had known issue of printing warnings to console (sockjs host check)

quickly tested (npm test, demo)

package.json

@@ -91,11 +91,11 @@
     "tslint-loader": "^3.5.3",
     "typedoc": "^0.13.0",
     "typescript": "^2.6.1",
-    "uglifyjs-webpack-plugin": "^2.0.0",
+    "uglifyjs-webpack-plugin": "^2.1.1",
     "underscore-template-loader": "^1.0.0",
     "webpack": "^4.25.0",
     "webpack-cli": "^3.0.8",
-    "webpack-dev-server": "3.1.11",
+    "webpack-dev-server": "3.1.14",
     "webpack-merge": "^4.1.2",
     "webpack-visualizer-plugin": "^0.1.11"
   },