rolling deployments

@obernal @gcobr adding a deployBeanstalkVersionZeroDowntime that does exactly that for environments that have beanstalk scripts that wait at application deploy time depending on their 'placement' in the autoscaling group instance ordering. The plugin is currently configured just for beanstalk environments with 2 instances, setting the desired capacity to 3 and waiting until all instances in the environment's autoscaling group are deemed healthy before continuing with the deployment procedure. This task is only for existing environments.