Add a scheme to check hosts.yaml

[RandyLevensalor]

Check the input in hosts.yaml with a proper schema.

[willtome]

Using the proposed hosts structure from #253 the syntax of the inventory will be validated by Ansible. Within the playbook, the assert and fail module could be used in conjunction with Magic Variables can be used to validate the correct groups exist. Once settled on, documentation of the hosts file format would be helpful as well