0.5.0 - Pinnable version release - Terraform 0.12 support

Allow use of 3 availability zones (#23)

* Allow use of 3 availability zones after terraform-providers/terraform-provider-aws#9398

* Update module documentation

* Move zone_awareness out of zone_awareness_config

* Add an extra az to th tfvars

* Revert "Add an extra az to th tfvars"

This reverts commit cdc0d26b018cfa48ec4733e19b72b90e9d0eb158.