allow "hotfix" deploys

a hotfix deploy is similar to a normal deploy, except:
- the maintenance page is not shown
- db migrations are not run
- load notifications are not run

The app remains available until the deploy is completed, at which point the symlink is moved and Passenger restarts the app.
pretty output

Suppresses the default verbose output and gives the pretty. The old verbose mode can be enabled with the `verbose=true` env var.
Merge pull request #66 from grahamb/hotfix-restart

Allow hotfix deploy