Version 3.1.0

Libraries

• Use gherkin 5.0 [GH-200]
• Support Ruby 2.5.0 [GH-201]
  • Drop 2.1 [GH-191]
• Support RSpec 3.7.0 and 3.6.0 [GH-197]

Fix

• Add license to gemspec [GH-193]
  • Thanks @koic
• Suppress warning [GH-195]
  • Thanks @swamp09