Drop support for the rest of EOL'd rubies

Author: deivid-rodriguez

.travis.yml

@@ -4,10 +4,6 @@ env:
     - "CC_TEST_REPORTER_ID=faa393209ff0a104cf37511a9a03510bcee37951971b1ca4ffc2af217851d47e"
 language: ruby
 rvm:
-  - 2.0
-  - 2.1
-  - 2.2
-  - 2.3
   - 2.4
   - 2.5
   - 2.6

Gemfile

@@ -8,7 +8,7 @@ gemspec
 group :development do
   gem 'bundler'
   gem 'rake',             '>= 10.5'
-  gem 'rdoc',             Gem::Version.new(RUBY_VERSION) < Gem::Version.new('2.2.2') ? '< 6' : '>= 6'
+  gem 'rdoc',             '>= 6'
   gem 'RedCloth',         RUBY_PLATFORM == 'java' ? '= 4.2.9' : '>= 4.0.3'
   gem 'rspec',            '~> 3.9.0'
   gem 'shoulda-context',  '>= 1.2.1'

README.markdown

@@ -15,7 +15,7 @@ You put your code in, and you get it back colored; Keywords, strings, floats, co
 
 ### Dependencies
 
-CodeRay needs Ruby 2.0+. It also runs on JRuby.
+CodeRay needs Ruby 2.4+. It also runs on JRuby.
 
 ## Example Usage
 

README_INDEX.rdoc

@@ -26,7 +26,7 @@ floats, comments - all in different colors. And with line numbers.
 
 === Dependencies
 
-CodeRay needs Ruby 2.0+. It also runs on Rubinius and JRuby.
+CodeRay needs Ruby 2.4+. It also runs on Rubinius and JRuby.
 
 
 == Example Usage

coderay.gemspec

@@ -20,7 +20,7 @@ Gem::Specification.new do |s|
   s.license = 'MIT'
 
   s.platform              = Gem::Platform::RUBY
-  s.required_ruby_version = '>= 2.0.0'
+  s.required_ruby_version = '>= 2.4.0'
 
   readme_file = 'README_INDEX.rdoc'