Stop requiring d3 in ChartwerkPod constructor

[jonyrock]

As comment says in https://github.com/chartwerk/base/blob/master/src/index.ts,

abstract class ChartwerkPod<T extends TimeSerie, O extends Options> {
// ...
  constructor(
    // maybe it's not the best idea
    protected _d3: typeof d3, 
    el: HTMLElement,
// ...
  ) {

it's not the best idea, but not "maybe". Why do you really need this d3 param?

Is it because you can't compile lib otherwise? Well, I think it doable....