This introduces a new class for managing ALBs. The API is different from

that of the old Elastic Load Balancer, and requires a different class.

Consumers can choose which class suits their needs.
This comes with some new utility functions for both types of load

balancers for checking registration and health state and waiting until

instances are marked as healthy or unregistered.

Made use of this in the RBCommons fabfile to handle deployments.