Documentation
Refactor and generalize node_manager

* Now supports instance typs other than taskworkers - only check the queue
  when deleting taskworker arrays
* Moved RightScale API client instantiation to a reusable method
elb_manager manager script for adding/removing server arrays from ELBs

Adding a new elb_manager manager script to work in conjunction with the node_manager.
This adds or removes entire server arrays to or from ELBs and is intended for red/black
style deployments.