pom.xml: updated liquibase to 3.2.0

@see http://blog.liquibase.org/2014/01/liquibase-3-1-0-released.html
@see http://blog.liquibase.org/2014/01/liquibase-3-1-1-released.html
@see http://blog.liquibase.org/2014/06/liquibase-3-2-0-released.html

No functional changes.