code: function _fetchSubreddit(subreddit) {
    const reducer = (prev, {data: {url}}) => prev.push(url) && prev;
    const jsonUri = `https://www.reddit.com/r/${subreddit}/.json`;
    return fetch(jsonUri)
      .then((res) => res.json())
      .then((res) => res.data.children.reduce(reducer, []))
      .then((urls) => ({subreddit, urls}));
  }
docs: Internal method to fetch the JSON feed and extract the URLs.
  @private
  @param  {String} subreddit Subreddit name to fetch JSON feed for.
  @return {Object} An object containing the subreddit name as a key, and links as a nested array.