Artifact management for spec documents.

I think it's for our best interest to utilize version management tool like
git and github in the process of generating and managing specs.
W3C even has an official guiideline on that matter.

http://w3c.github.io/specs.html

Due to the distributed nature of git, it should be pretty easy to establish
a more formal, official version of a repository once we get started working
on a more adhoc version.

I took the liberty of generating a public repository for openkeychain spec
under my username at github.

https://github.com/shepelt/openkeychain-spec

I'll share my work there once I'm finished with the internalization process
of the document.