Update wdl4s version from 0.14 to 0.15
Update wdl4s version from 0.14 to 0.15

broadinstitute/cromwell,broadinstitute/cromwell,broadinstitute/cromwell,ohsu-comp-bio/cromwell,ohsu-comp-bio/cromwell,ohsu-comp-bio/cromwell,broadinstitute/cromwell,broadinstitute/cromwell