colourScale documentation needs updating

[ellisp]

This may be as simple as changing https://github.com/mbostock/d3/wiki/Ordinal-Scales in the current helpfile to point to somewhere else, but I'm not sure exactly where.

Meanwhile, the Stack Overflow answer I used in the past to remind me how to control colours doesn't work any more.

I think this is just a matter of updating documentation and examples but don't know enough about the changes in D3 to know quickly how to do it myself.

[ellisp]

Noting, old code I had like:

colourScale = JS('d3.scale.ordinal().range(["#7d3945","#e0677b", "#244457"])')

now works if it is changed to:

colourScale = JS('d3.scaleOrdinal().range(["#7d3945","#e0677b", "#244457"])')