Converts the 'duedate' field from the ISO format (YYYY-MM-DD) into the JIRA required format (d/MMM/yy) in create_issue and progress_workflow_action_safely. This is necessary because while JIRA requires the later, it gives the former in getIssue. Thanks to Andrey Belous for alerting me about this.
Adds a perlcritic test and placates some of its criticisms.