beaker 3.36.0

Fixed

• Raise ArgumentError when passing role = nil to only_host_with_role() or find_at_most_one_host_with_role()
• Use install_package_with_rpm in add_el_extras

Added

• Installation instructions for contributors
• Markdown formatting guidelines for docs/
• Glossary for project jargon in docs/concepts/glossary.md
• Use AIX 6.1 packages everywhere for puppet6