pom.xml(liquibase-maven-plugin): output SQL statements to stdout.

Now liquibase:updateSQL and liquibase:rollbackSQL will write its
output to stdout instead of file inside target/ directory.

[ci skip]
Revert ".travis.yml: removed --quiet flag from dependency installation command."

This reverts commit bfdf8051b3e15d9e48b30435dd02cedefcfebdcd.

No needed anymore: was added to debug why build fails under Travis CI.