nest deprecated

[SaFrMo]

Absolutely love this tutorial, thanks for connecting the dots on D3's data structures and Vue's reactivity!

One thing I noticed while working through was that the nest function has been deprecated in favor of group and rollup. I was able to arrive at the same result with some changes in the Chart component:

// replace this:
const nestedTweets = d3
    .nest()
    .key(d => d.user)
    .entries(this.tweetData);

// with this:
const nestedTweets = d3.group(this.tweetData, d => d.user)

// replace this:
const packableTweets = { id: 'All Tweets', values: nestedTweets }
return d3
    .hierarchy(packableTweets, d => d.values)
    .sum(d =>
        d.retweets ? d.retweets.length + d.favorites.length + 1 : 1
    )

// with this:
return d3
    .hierarchy(nestedTweets)
    .sum(d =>
        d.retweets ? d.retweets.length + d.favorites.length + 1 : 1
    )