message: Upgrade polymer-bundler to 2.0.0-pre.2
diff: "sw-precache": "^4.2.0",
  "vinyl": "^1.1.1",
  "vinyl-fs": "^2.4.3",
  - "polymer-bundler": "2.0.0-pre.1"
  + "polymer-bundler": "2.0.0-pre.2"
  },
  "devDependencies": {
  "@types/chai": "^3.4.34",
  