Breaking change: Remove redundant packager entry point

Summary: We have too many ways to start the packager:
- react-native start
- npm start
- ./packager/packager.sh
- ./packager/launchPackager.command

This removes yet another one. According to the [npm docs](https://docs.npmjs.com/files/package.json)
this creates `/usr/local/bin/react-native-start`. Let's kill it.

public

Reviewed By: martinbigio

Differential Revision: D2559953

fb-gh-sync-id: e3b41a0622e6168fe686cdf9c93714dbf02f5965

package.json

@@ -46,9 +46,6 @@
     "lint": "eslint Examples/ Libraries/",
     "start": "./packager/packager.sh || true"
   },
-  "bin": {
-    "react-native-start": "packager/packager.sh"
-  },
   "dependencies": {
     "absolute-path": "^0.0.0",
     "babel-core": "^5.8.23",