Published, v1.6

Unless future versions usurp this one, then this is the latest version to be read in conjunction with the published version online.

Published, v1.5

Unless future versions usurp this one, then this is the latest version to be read in conjunction with the published version online.

Accepted, pre-proofing v1.4

Unless changes are made at the proofing stage then this is the version for publication too.

Post-review v1.3

update

Post-review v1.2

Supplementary information added.

Post-review v1.1

Update README.md

v1.0

This release coincides with submitting the manuscript for publication.