Upgrade Travis and Rultor to Java 8

See #1225, release log:

• 4240c84 by @yegor256: #1225 java 8
• 8f1d38f by @tannakartikey: #1195 added Postgres configur...
• 2f1a7a1 by @yegor256: TEAM.md removed
• f1b2c1e by @tannakartikey: #1197 build number creation ex...
• ef7795d by @yegor256: safer deploy
• 4b45dbb by @yegor256: Merge pull request #1217 from ...
• ba2407d by @filfreire: #1216 add CONTRIBUTING.md
• 733f47d by @yegor256: badge

Released by Rultor 1.67, see build log