before and after lambdas

After giving this some thought, here is what I've come up with:

    deployment.before_activate_maintenance_mode = lambda {|deployment| %x(curl before) }
    deployment.after_warm_instance = lambda {|deployment| %x(curl after) }

    deployment.deploy

There is an option to do before or after anything with a lambda that gets passed the deployment.  It lets folks do anything they want at any step.  In addition you can remove steps.