Update the Peril description.
Don't claim it's easy.
Update the README setup instructions.
You usually don't need the Mailgun key.
Use peril.example.yml to trigger syntax highlights.
Update other references to the example yml.
Write up a quick Contributing guide.
Update the examples you have to mess with.
Merge pull request #16 from rackerlabs/update-readme

Update README and write a CONTRIBUTING guide.