migrate to Dokku

See #27, release log:

• 19391ac by @yegor256: #27 dokku
• a1d72d2 by @yegor256: fixed versions for rultor
• 0b4c7c2 by @yegor256: elegantobjects.org HTTPS
• 74d8df8 by @yegor256: Sixnines.io HTTPS
• 2aa6d8c by @yegor256: Sixnines.io HTTPS
• dad5221 by @yegor256: readers
• 38d0899 by @yegor256: IntelliJ badge changed
• 5126697 by @yegor256: .github templates
• cc88981 by @yegor256: 0pdd config
• e2624d7 by @yegor256: TEAM.md removed
• b8104ec by @yegor256: safer deploy
• d20cced by @yegor256: zerocracy badge

Released by Rultor 1.68.6, see build log