Update Redux setup

[lyndsherb]

Updates the React/Redux integration to be more streamlined.

Previously, the generator was calling this.context.store.getState() or this.context.store.dispatch() in a lot of places to trigger the actions. This is repetitive, boring, and not exactly best practice. This StackOverflow answer explains it like so:

{...} Primarily because it really muddies the line between container and presentational components. Presentational components don't need access to store, and there are other methods to do this which don't have this (albeit pedantic) drawback.

react-redux, however, provides us with a handy connect function which allows us to hook the Redux state and the actions into the props of our application. This allows us to pass the application state down as necessary.

The presentational components have also been updated to be function components rather than Class components. Functional components are simpler than Class components, and as such are a better fit when all we want to to is render out JSX. More information can be found in this article by Dan Abramov.

The setup itself was helped along with this article from Code Like A Girl.

I also updated the tests to provide more thorough examples, such as testing the React output and the return on both actions and reducers.

Todo

• Add babel-plugin-transform-object-assign and redux-mock-store to Magepack SDK; one for browser compatibility, one for better testing.
• Ensure this can be easily integrated into Magento as expected
• Ensure the store can be accessed outside the app

[convenient]

I'm not too familiar with this redux stuff but your changes and reasoning do look sensible.

I'd ask that you try and get a review from torrey and nick, perhaps chase up with a PM if you need their time.

[nick-price-amp]

Could still use arrow funcs here? If only for consistency

[nick-price-amp]

Could just do:

return ({
  ...state,
  selected: state.id === action.id
});

It's not really clearer tho tbf