[Rivet] Move bootstrap into main repository for versioning?

[David Grellscheid]

Hi Andy,

> - in the Rivet repo the tag indicates what repo state corresponds to the
> release with that number, and should generally be unchanged once made
> 
> - in the bootstrap repo the tag tells users how to download a script
> which will build the Rivet version named in the tag. If the script is
> found to be buggy for that release, we can bugfix it and move the tag to
> the appropriate revision. (The named branch is a good idea.)

Yes, but no tag movement is actually involved, since the branch name
itself works as a tag to its head node.

> If everyone is happy, I will release the new Rivet and YODA this afternoon.

I have made some minor fixes to both today, and am running the static
clang analyzer as I write this. I'll let you know when it's done.

  David