This commit is not precisely atomic, but the changes have evolved, summary: * The ENV-based interface has been moved upwards, the generator has now a conventional initializer. * RAILS_VERSION is now assumed to be a Git tag. A blank RAILS_VERSION means edge guides. * In consequence, the EDGE env variable is gone. * The "local" version is also gone, the current SHA1 is computed for edge guides. * Assumes guides are generated from a repo checkout (time ago users could generate them from gems.) * The WARNINGS flag is gone in consequence, you cannot disable warnings. * The `api_link` Markdown helper is fixed. * Docs about usage have one single place: rake guides:help. * Links in guides have been revised.