Release Version 1.0.0

Here it is. Version 1.0.0 of the specification. We didn't discuss this before, but I thought @chrisdew suggestion to use SemVer seems pretty reasonable for me. Even though it is a Spec and not Code, it's still possible to reason about breaking/non-breaking changes.

Also I decided to delete the draft versions. They are still accessible through git, but I don't think we need them floating around in the main directory.

Lastly I decided to call it "readme.md", so that it's also easily readable on GitHub. And since there's only one MD file in the repo, there is no confusion which document is the current spec.

Are you fine with that? I'm excited about this. This wil close  #13

Best,
Finn