Automatically reload when package.json changes

[niieani]

Same problem as below, along with a solution:

facebook/create-react-app#186
facebook/create-react-app#336
facebook/create-react-app#349

[valscion]

It's now possible to just use react-dev-utils package on npm and fetch the WatchMissingNodeModulesPlugin from there.

I'm not 100% sure whether webpack plugins can contain other plugins as well, though.