* New module - elb_target
* Work to add deregister functionality
* Add jurajseffer work on waiting for status change
* List the set of statuses as a choices list
* default target_status_timeout is 60
* Add 'unavailable' as a target status choice per API docs
* Add support to remove targets that are in unused state
* add support for availability zone selection
Fix deregistering targets from used target groups
Fix waiting for unused state for targets that have started deregistering
