Publish2maven - gradle scripts for publishing jars to Maven Central repo

Note that to make the tasks 'signing' and 'uploadArchives' work, we still a private gradle.properties which contains the  sensitive information such as gpg-secret-key for signing jars and sonatype username/password for uploading jars to remote maven repo.  And thus, on internet, to make travis-ci builds pass for aws-mock, we comment signing tasks and only upload artifacts to a local maven repo.