Remove tests for unsupported ruby and rails versions

Author: gingermusketeer

.travis.yml

@@ -4,20 +4,10 @@ cache: bundler
 before_script: bundle install --jobs=3 --retry=3
 
 rvm:
-  - 2.2
-  - 2.3
-  - 2.4
   - 2.5
   - 2.6
+  - 2.7
 
 gemfile:
-  - gemfiles/Gemfile.rails-4-2-stable
-  - gemfiles/Gemfile.rails-5-0-stable
-  - gemfiles/Gemfile.rails-5-1-stable
   - gemfiles/Gemfile.rails-5-2-stable
   - gemfiles/Gemfile.rails-6-0-stable
-
-matrix:
-  exclude:
-    - rvm: 2.3
-      gemfile: gemfiles/Gemfile.rails-4-2-stable

gemfiles/Gemfile.rails-5-0-stable

@@ -2,7 +2,7 @@ source "https://rubygems.org"
 
 gemspec path: ".."
 
-gem "rails", git: "https://github.com/rails/rails.git", branch: "4-2-stable"
+gem "rails", git: "https://github.com/rails/rails.git", branch: "6-0-stable"
 
 group :test do
   gem 'capybara', '>= 2.1'