Add demo environment, bump to 0.2.2.alpha

Using a demo environment on current apps, which is like production, but it
doesn't have real client data on it.

Ideally I'd like to be able to specify your own set of binstubs for any
number of environments ("beta", "rollout", etc.), but I don't think
installing those stubs through Rubygems isn't going to be the right
approach. Heroku-binstubs can build less-capable binstubs, but they are
missing the `migrate` command which is indispensable.