using *zip*/archive.zip as default for :jenkins_artifact_file

deploy fails with `SSHKit::Runner::ExecuteError: Exception while executing on host <deploy host>: can't convert nil into String` when `:jenkins_artifact_file` not specified

using `*zip*/archive.zip` as default value

if `:jenkins_artifact_file` option not specified - unzipping artifact content and moving to release path.
Preference here would be to keep this, so the revision reported by Capistrano sets these build numbers more clearly apart from any Git/SVN/Hg-based deployments.