Ruby Idioms: add Blue-Green Deployment section
Ruby Idioms: add reference to This Agile Life
Ruby Idioms: add Honorable Mentions

These are things I would have liked to have talked about,
but didn't have time to cover, or didn't have much interesting
to say about them.
Ruby Idioms: Show non-idiomatic Ruby first
Ruby Idioms: last-minute changes

Quite a few small-to-medium changes.
Ruby Idioms: use external URLs

Make it work for people pulling down from the link.