(devel) Playbooks and tasks now check themselves for typos a bit better

[Michael DeHaan]

If you type "var" for "vars", or try to use a keyword that Ansible doesn't know about, it will now yell at you.

If you were doing things like:

"comment: this is a comment"

You should switch to YAML comments

# YAML comments look like this.

This was done to prevent the whole class of questions in the form of:

- Ansible is broken! Here is a snippet of my playbook!
- What does your playbook look like?
- Here it is
- It's "vars_files" not "var_files"!
- It's still not working!
- Let me see your playbook…

In the event that I have somehow forgotten something legal that should be in the list, and you think it's yelling about you about something
valid, let me know.

(Grep for VALID_KEYS in the source if you are curious where this is)

--Michael