[WIP] Add Analytics

So this is a careful subject, very much welcome to review. I want some basic tracking so we know how users are using roots and can improve it accordingly. There are a few precautions taken here. First, there's a post-install message added that notifies the user about the presence of analytics. Second, there's a class method on `Roots` you can use to flip the analytics tracking off, as well as a command you can run from the cli. Third, I was careful not to track any info like folder paths etc that would de-anonymize the data. Everything is dumped to keen, from which we can make a little dashboard.