Feature requests

[weibeld]

Requested features for v0.3:

• Choose Kubernetes version (Choose k8s version #1)
• Pass custom user data to EC2 instances (Provide User Data Option #2)
• Add EC2 instance IDs to cluster_nodes output (added a couple of extra features #4)
• Add availability zone as input parameter (added a couple of extra features #4)
• Add availability zone to cluster_nodes output (added a couple of extra features #4)
• Add support for autoscaling groups (Kubeadm on Autoscaling Groups. #7)
• Additional SSH key options:
  1. Use an existing AWS EC2 key pair (specify name of key pair on AWS and private key file on local machine)
  2. Create keys on the fly (e.g. use [tls_private_key])(https://registry.terraform.io/providers/hashicorp/tls/latest/docs/resources/private_key)
  3. Provide both public and private key on the local machine (already implemented)