Drop support for Rails 4.x series

Author: andrehjr

.travis.yml

@@ -1,38 +1,19 @@
 language: ruby
 rvm:
-  - 2.0
-  - 2.1.10
   - 2.2.2
   - 2.3.8
   - 2.4.9
   - 2.5.7
   - 2.6.5
 
 gemfile:
-  - gemfiles/4.2.gemfile
   - gemfiles/5.0.gemfile
   - gemfiles/5.1.gemfile
   - gemfiles/5.2.gemfile
   - gemfiles/6.0.gemfile
 
 matrix:
   exclude:
-  - rvm: 2.0
-    gemfile: gemfiles/5.0.gemfile
-  - rvm: 2.0
-    gemfile: gemfiles/5.1.gemfile
-  - rvm: 2.0
-    gemfile: gemfiles/5.2.gemfile
-  - rvm: 2.0
-    gemfile: gemfiles/6.0.gemfile
-  - rvm: 2.1.10
-    gemfile: gemfiles/5.0.gemfile
-  - rvm: 2.1.10
-    gemfile: gemfiles/5.1.gemfile
-  - rvm: 2.1.10
-    gemfile: gemfiles/5.2.gemfile
-  - rvm: 2.1.10
-    gemfile: gemfiles/6.0.gemfile
   - rvm: 2.2.2
     gemfile: gemfiles/6.0.gemfile
   - rvm: 2.3.8

gemfiles/4.2.gemfile

@@ -40,5 +40,5 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'rspec',       '~> 3.7'
   s.add_development_dependency 'pry',         '~> 0.10'
   s.add_development_dependency 'fakeredis',   '~> 0.7'
-  s.add_development_dependency 'rails',       '>= 4.2'
+  s.add_development_dependency 'rails',       '>= 5.0'
 end