remove ability to set styles from data

[boygirl]

This PR deprecates the ability to define style attrs directly on the data object. This will be a breaking change, but the upgrade path is minimal:
If your data object looks like

data={[
  { x: 1, y: 1, fill: "red", opacity: 0.2 }, 
  ...
]}

Add the following functional styles:

style={{ data:  { fill: (d) => d.fill, opacity: (d) => d.opacity } }}

and everything will work as before