Update the CI build to test this gem against the latest versions of Nodejs, Ruby, and Rails.
Considerations
The test suite includes test Rails apps, using configurations as generated by various versions of Rails. The majority of the changes in this PR consist of deleting the test apps for Rails 4.2 and 5.1, and adding test apps for Rails 5.2 and 6.1.
Change
Update the CI build to test this gem against the latest versions of Nodejs, Ruby, and Rails.
Considerations
The test suite includes test Rails apps, using configurations as generated by various versions of Rails. The majority of the changes in this PR consist of deleting the test apps for Rails 4.2 and 5.1, and adding test apps for Rails 5.2 and 6.1.