commons-lang dependency improvements

This PR consists of two commits. The first was essential to remove a build failure. See the commit log for details. The second is nice to have given that commons-lang3 has been out for nearly two years.

I'm not sure of the protocol here. Since your PR for add-debian-support-with-1.8 has not yet been merged into https://github.com/TrigonicSolutions/gradle-rpm-plugin, it seemed safer to send the PR here rather than there.

I am happy to resubmit the PR to https://github.com/TrigonicSolutions/gradle-rpm-plugin after your PR has been merged, if you prefer. It depends how likely your PR is to be accepted I guess.