Added top-level npm scripts for building and testing devtools-core/standalone

Author: bvaughn

package.json

@@ -40,12 +40,14 @@
  "build:extension": "npm run build:extension:chrome && npm run build:extension:firefox",
  "build:extension:chrome": "node ./shells/chrome/build",
  "build:extension:firefox": "node ./shells/firefox/build",
+ "build:standalone": "cd packages/react-devtools-core && npm run build",
  "deploy": "cd ./shells/theme-preview && ./build.sh && gh-pages -d .",
  "lint": "eslint .",
  "postinstall": "lerna bootstrap",
  "test": "node --harmony ./node_modules/.bin/jest",
  "test:chrome": "node ./shells/chrome/test",
  "test:firefox": "node ./shells/firefox/test",
+ "test:standalone": "cd packages/react-devtools && npm start",
  "typecheck": "flow check"
  },
  "jest": {