Adds the Sequel::Migration and Sequel::Migrator classes, which allow the user to easily group schema changes and migrate the database to a newer version or revert to a previous version.
To load the extension:
Sequel.extension :migration
Related modules: Sequel::Migration, Sequel::SimpleMigration, Sequel::MigrationDSL, Sequel::MigrationReverser, Sequel::MigrationAlterTableReverser, Sequel::Migrator, Sequel::IntegerMigrator, Sequel::TimestampMigrator