Hack of the crossfilter example to work with d3js v4
It is very annoying that the original crossfilter/d3 example works only with d3 v3. Many changes have occured with d3js v4, among them: brushes, scales, format. And it is a bit more complex than just renaming.
This is a quick and dirty first attempt to adapt the example. There are still few behavioral discrepancies compared to the original one. But it should be usuable from my point of view.