Update license info

[jangondol]

LICENCE.md says the license is "Attribution-ShareAlike 4.0 International" while README.md claims "Except where otherwise noted, this work is licensed under a Creative Commons Attribution 4.0 International License."

This should be made consistent.

Also, while we are at it, is it possible to also consider renaming LICENCE.md to LICENSE.md to make spelling consistent? U.S. version is standard, even this repository uses it (see README.md cited above), just not consistently.

[rchampieux]

Thanks @jangondol - good catch. You're correct, we intended to communicate a CCBY 4.0 for the entire repo.

Interestingly, that's not coming up as a template option when I go to create a new LICENSE.md file. I will fix when I have a few more minutes to work on this. For now, I've killed the original license file.