Add Travis CI support

[filiphr]

• Add Travis build with matrix for
  • openjdk8
  • oraclejdk8
  • openjdk10
  • openjdk11
  • openjdk-ea
• Use explicit maven compiler source and target version (source and target 1.5 have been removed from JDK10)
• Use latest version of Lombok (1.18.0) that works on Java 10
• Use latest version of Kotlin (1.2.51) that works on Java 10
• Use mapstruct 1.3.0-SNAPSHOT
• Manually symlink CA certs for openjdk10 to solve problem with https connections with sonatype_snapshots