Update to 5.x

[gaeljw]

This PR aims to upgrade Cucumber dependency to 5.X, actually 5.6.0.

Content:

• update code to be compatible with Cucumber 5.6.0
• added some tests (mainly copied from Cucumber Java)
• add documentation in README about major changes:
  • move all classes under io.cucumber.scala to be more consistent with Cucumber Java
  • parameters change in Before/After hooks to be consistent with Cucumber Java
• upgrade Scala versions, Scala Maven plugin and Groovy

The breaking changes are open to discussion but I feel:

• it helps convey the idea that there is major changes with the upcoming 5.x release (I would like to include the fix for cucumber-scala instantiates step definition classes per test JVM instead of per scenario #1 as well, PR coming soon...)
• it makes Cucumber Scala more consistent with Cucumber Java and will ease developers to contribute

[mpkorstanje]

Looks good to me.

[aslakhellesoy]

Hi @gaeljw,

Thanks for your making your first contribution to Cucumber, and welcome to the Cucumber committers team! You can now push directly to this repo and all other repos under the cucumber organization! 🍾

In return for this generous offer we hope you will:

• ✅ Continue to use branches and pull requests. When someone on the core team approves a pull request (yours or someone else's), you're welcome to merge it yourself.
• 💚 Commit to setting a good example by following and upholding our code of conduct in your interactions with other collaborators and users.
• 💬 Join the community Slack channel to meet the rest of the team and make yourself at home.
• ℹ️ Don't feel obliged to help, just do what you can if you have the time and the energy.
• 🙋 Ask if you need anything. We're looking for feedback about how to make the project more welcoming, so please tell us!

On behalf of the Cucumber core team,
Aslak Hellesøy
Creator of Cucumber