facetting

[earowang]

New args rows = NULL and cols = NULL to support small multiples.

[casperhart]

Where's this example from? And is this example animated, or is it a snapshot that's been exported?

And would the rows and cols args just repeat the same tour in all 3 of the tiles, and leave the colouring to the user (e.g. using the box-selection)? Or would there be args for the colour too?

If we want to support crosstalk as well, we'd need to be very careful about how this is implemented so they don't conflict.