Tutorial and Spec versioning

Created by: wks

I am evaluating http://readthedocs.org/ . A µVM tutorial is being written.

Jekyll seems to bias strongly towards blogging and the structures (including a table of content and a per-page sidebar of the outline) are not automatically handled.

There should be a common version scheme for the spec, the refimpl and the tutorial. I propose using the major version "2" for the current version. The tutorial will target the "main" version (currently "2").

GitHub Wiki sucks (very primitive structure support, no table of content). Considering migrating the specification (https://github.com/microvm/microvm-spec/wiki) back to Sphinx/reStructuredText if readthedocs.org is proved useful.