FEATURE: Nested components

[dkaoster]

Closes #31

TYPE OF CHANGE

After some discussion and testing on our end, we've decided to go with this approach to solve the issues outlined in #31. Specifically, we modified this repo to allow for a nested hierarchy when creating elements based on data.

PROBLEM

Sometimes, we would like for our datasets to generate svg elements more than a single node. For instance, we may want to wrap a rect with an anchor, or include text with a shape.

SOLUTION

The solution is to allow components to be nested. That way, we can use something like

<AnimatedDataset
  dataset={['Hello World', 'Goodbye World']}
  tag="a"
  attrs={{ href: "#test" }}
  keyFn={t => t}
  disableAnimation
>
  <AnimatedDataset
    tag="text"
    attrs={{ text: t => t }}
    keyFn={t => t}
    disableAnimation
  />
</AnimatedDataset>

NOTES

This should be fully backward compatible with the current API and introduce this feature with no breaking changes.