Pin consul image to 1.15.4

In Release v3.0.0, the consul image is pinned to 1.15.4 as opposed to latest in the previous release.

Upgrade to Terraform v0.12.9

Merge pull request #2 from asicsdigital/terraform12

Update Module to Terraform 0.12.9

Use the fitnesskeeper/consul-sidecar image

• rename image from healthcheck to sidecar - since we are doing all kinds of non-health check stuff in the image.
• Updates IAM permissions to allow the sidecar to do it's thing, in particular

+      "cloudwatch:PutMetricData",
+      "ecs:DescribeClusters",
+      "ecs:UpdateContainerInstancesState",
+      "ecs:DescribeContainerInstances",

Initial Release

This is the initial release of this module. It should allow you to more easly add sidecare helper containers to your Consul agents that run out of Docker.