Merge branch 'master' into kramdown-v1-17-0

.rubocop.yml

@@ -16,7 +16,7 @@
 # If you disable a check, document why.
 
 AllCops:
-  TargetRubyVersion: 2.2
+  TargetRubyVersion: 2.3
   Exclude:
     - 'bin/**/*'
     - 'script/**/*'

.travis.yml

@@ -1,6 +1,5 @@
 language: ruby
 rvm:
-  - 2.2
   - 2.3
   - 2.4
   - 2.5

github-pages.gemspec

@@ -5,7 +5,7 @@ require File.expand_path("../lib/github-pages/plugins", __FILE__)
 require File.expand_path("../lib/github-pages/version", __FILE__)
 
 Gem::Specification.new do |s|
-  s.required_ruby_version = ">= 2.0.0"
+  s.required_ruby_version = ">= 2.3.0"
 
   s.name                  = "github-pages"
   s.version               = GitHubPages::VERSION