CI: Use 2.4.6, 2.5.5, 2.6.3
CI: Use 2.4.6, 2.5.5, 2.6.3

  - drop defunct Travis option sudo: false - see https://blog.travis-ci.com/2018-11-19-required-linux-infrastructure-migration
capistrano/capistrano,capistrano/capistrano