relicense all code to apache-2

It has recently become clear that the MIT license leaves much to be desired – and when we see spot a flaw in our ecosystem, I think we should fix it.

I was thinking we switch all of our projects over to `Apache-2`. It's clearer language than MIT and has an explicit portion on patent licensing. Chances are also big that people have heard of this license before, and know what it stands for. More on this in [/dev/lawyer/oss-business-perception-report](https://writing.kemitchell.com/2017/03/29/OSS-Business-Perception-Report.html).

@choojs/trainspotters thoughts?

The issue names no files, tests, or entry points. Start by reviewing the nine-comment discussion and identifying which projects and license files are in scope; done requires agreement on the Apache-2 relicense and completion across all affected projects.

Written by the indexing model from the issue text.