React-D3 is no longer maintained

[nhooey]

Search for "NOT MAINTAINED" on their GitHub page:
https://github.com/react-d3

There's also a broken documentation link issue from 2016:
react-d3/react-d3.github.io#13

It's probably best to mention that this library is abandoned.

[damntrecky]

I will add a pull request to fix this!