message: Upgrade polymer-bundler to 2.0.0-pre.8
diff: "parse5": "^2.2.2",
  "plylog": "^0.4.0",
  "polymer-analyzer": "2.0.0-alpha.28",
  - "polymer-bundler": "2.0.0-pre.7",
  + "polymer-bundler": "2.0.0-pre.8",
  "polymer-project-config": "^2.0.0",
  "sw-precache": "^4.2.0",
  "vinyl": "^1.1.1",
  