Support react-native 0.42

[uk-ar]

react-native-storybook v2.2.3 with React Native v0.42 throws exceptions bellow.

Looking for JS files in
   /Users/yuuki/CycleReactNativeEx/storybook


React packager ready.

Loading dependency graph, done.
webpack built dfe665bec475801da0ee in 7585ms
(node:16333) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 7): UnableToResolveError: Unable to resolve module `react-native` from `/Users/yuuki/CycleReactNativeEx/storybook/index.android.js`: Module does not exist in the module map or in these directories:
  /Users/yuuki/CycleReactNativeEx/node_modules

This might be related to https://github.com/facebook/react-native/issues/4968
To resolve try the following:
  1. Clear watchman watches: `watchman watch-del-all`.
  2. Delete the `node_modules` folder: `rm -rf node_modules && npm install`.
  3. Reset packager cache: `rm -fr $TMPDIR/react-*` or `npm start --reset-cache`.
(node:16333) DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

This problem may affected by facebook/react-native#12659 or facebook/react-native@bce6ece.
This Pull Request works for me both React Native v0.42 and v0.41.

[mlabrum]

+1 this solved my issue on 0.42 :)

[thani-sh]

Published RN Storybook v2.2.4 with this fix

[uk-ar]

Thanks @mnmtanish