message: add unpacked build option for mac
diff: "dist-mac": "npm run prebuild && build --mac",
  "dist-win": "npm run prebuild && build --win --x64",
  "dist-win-x86": "npm run prebuild && build --win --ia32",
  + "unpacked-mac": "npm run prebuild && build --mac --dir",
  "unpacked-win": "npm run prebuild && build --win --x64 --dir",
  "unpacked-win-x86": "npm run prebuild && build --win --ia32 --dir",
  "prebuild": "npm run lint && npm run test && npm run browserify-preload",
  