Change to CC0

[kemitchell]

@danielhusar, @sschuberth, are you willing to apply Creative Commons CC0 to your contributions to this package, as well? See 16d0a9f

I see that you've each made only one or two commits here, but they look significant! I'm not sure what, if any, of the current code derives from yours. But it would be nice to be clear about the terms change.

[sschuberth]

I'm fine with re-licensing my contributions under CC0.

[ghost]

Better yet WTFPL and fuggetaboutit

By the way https://github.com/spdx/license-list-data/blob/master/json/licenses.json