test against all currently supported ruby versions

Author: formigarafa

.travis.yml

@@ -1,5 +1,7 @@
 sudo: false
 language: ruby
 rvm:
-  - 2.3.3
+  - 2.6.9
+  - 2.7.5
+  - 3.0.3
 before_install: gem install bundler -v 1.16.1

csv-safe.gemspec

@@ -19,7 +19,7 @@ Gem::Specification.new do |spec|
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ['lib']
 
-  spec.required_ruby_version = '>= 2.7.0'
+  spec.required_ruby_version = '>= 2.6.0'
 
   spec.add_development_dependency 'bundler', '>= 2.1.4'
   spec.add_development_dependency "rake", ">= 12.3.3"