Only import from d3-* modules

[jfsiii]

There are a few files which import from d3 which brings in all the d3-* modules even if they aren't used. While webpack & rollup can mitigate this, they still leave many unused functions.

Looking through the code I found these examples:

# src/lib/charts/bubble/BubbleD3.js
import { hierarchy, pack } from 'd3'

# src/lib/scale.js
import { scaleLinear, scaleBand, scalePoint } from 'd3'

# src/lib/charts/labels.js
import d3 from 'd3'

#src/lib/charts/pie/PieD3Svg.js
import d3 from 'd3'

# src/lib/charts/bubble/BubbleD3Svg.js
import d3 from 'd3'

I apologize for the noise if I've simply found some loose ends that aren't used/exported.

[plouc]

@jfsiii, no problem, thank you for raising that, I've removed all those files.