This PR enables testing against multiple Rails versions (6.0, 5.2, 5.1 and 5.0) using the appraisal gem. It creates one check for each combination of Ruby version and Rails version.
Tests with Rails 5.0 and 5.1 are currently failing because of the ActiveStorage config in the dummy application. Because #40 will remove this stuff, I will rebase this branch after #40 is merged.
This PR enables testing against multiple Rails versions (6.0, 5.2, 5.1 and 5.0) using the appraisal gem. It creates one check for each combination of Ruby version and Rails version.