message: Update Babel-related devDependencies to latest beta versions.
diff: "source-map": "~0.6.1"
  },
  "devDependencies": {
  - "@babel/core": "^7.0.0-beta.49",
  - "@babel/parser": "^7.0.0-beta.49",
  - "@babel/preset-es2015": "^7.0.0-beta.49",
  + "@babel/core": "^7.0.0-beta.51",
  + "@babel/parser": "^7.0.0-beta.51",
  + "@babel/preset-es2015": "^7.0.0-beta.51",
  "esprima-fb": "^15001.1001.0-dev-harmony-fb",
  "flow-parser": "^0.68.0",
  "glob": "^7.1.2",
  