PSR-15 Queue v1.2.0

Minor Changes:

• Added a Warning header to identify response messages from converted exceptions
• Removed the option to provide an exit status to QueueRequestHandler::respond()
• Added Composer command for development tools (PHP Mess Detector, Psalm Taint Analysis)

Maintencance:

• Updated dependencies

Full Changelog: v1.1.0...v1.2.0