Juju is on github

[Martin Packman]

Juju development is now done on github:

<https://github.com/juju/juju>

See the updated CONTRIBUTING doc for the basics. To land code you want
the magic string $$merge$$ in a comment on the pull request so the
jenkins bot picks it up.

Note that the bot is currently taking around three times as long to
run the tests, as we can't run suites in parallel due to mongo test
flakiness. We'll work on improving that, but feel free to find and fix
slow tests while you wait. :)

As a team we're going to have some pain and discovery this week,
please share any git tips and information you find useful as you go
along. Thanks!

Martin