v0.6.1

Changed

• The sqlate requirement is v0.4.1, whose Force writes a set's whole history prefix through
  the version. On v0.4.0, Service.Force forcing a set with more than one migration from 0 back
  to its head left a history every later Status, Verify, Up, Down, and Reset refused
  with migrate.ErrUnknownVersion. The service's own code is unchanged.