Bump version to 2.0.0
Bump version to 2.0.0

Seems like a big bump for a minor change but since I'm removing
Rails 2.3 support I want to stick to semantic versioning and do a
major non-backwards-compatible release.

rodovich/turnout,biola/turnout,biola/turnout,rodovich/turnout,ayann/turnout,ayann/turnout