(demo): Set more precise React/React-Native package version dependencies for Example (react-native-camera#679)

* Set more precise React/React-Native package version dependencies - In general, try to avoid breaking changes caused by >= - In particular, such a breaking change can be seen by testing the current Example app on Android with the existing package.json's and RN 0.43+, which causes errors in MainApplication public/protected method settings. * Revert changes to main package.json - Would erroneously break compatibility for main package - Leave precise dependencies only for Example app, since this does not impact compatibility in the same way

Author: abrahambotros

Example/package.json

@@ -6,8 +6,8 @@
  "start": "node node_modules/react-native/local-cli/cli.js start"
  },
  "dependencies": {
- "react": ">=15.4.0",
- "react-native": ">=0.40",
+ "react": "~15.4.0",
+ "react-native": "~0.40.0",
  "react-native-camera": "file:../"
  }
 }