Code changes for issue #89 on blog_robinwieruch_content.

Based on this comment by Matt Wright:

You can make your fetch hook cleaner by removing

const doFetch = url => {
setUrl(url);
};

and just returning setUrl like so

return [ ...state, setUrl ];

then change your hook call to

const [ data, doFetch ] = useDataApi(
'http://hn.algolia.com/api/v1/search?query=redux',
{ hits: [] },
);

And now you can rename "doFetch" to anything you want```

Doing exactly as Matt Wright said yielded an error for me, so I changed it as much as I needed to.

PR for changes to blog post: rwieruch/blog_robinwieruch_content#107