Drop Ruby 1 support

Author: amatsuda

README.md

@@ -167,7 +167,7 @@ end
 
 ## Supported versions
 
-* Ruby 1.8.7, 1.9.2, 1.9.3, 2.0, 2.1, 2.2, 2.3, 2.4 (trunk)
+* Ruby 2.0, 2.1, 2.2, 2.3, 2.4 (trunk)
 
 * Rails 3.0.x, 3.1.x, 3.2.x, 4.0.x, 4.1, 4.2, 5.0 (edge)
 

gemfiles/Gemfile.rails-3.1

@@ -2,9 +2,6 @@ source 'https://rubygems.org'
 
 gem 'railties', '~> 3.1.0'
 gem 'activerecord', '~> 3.1.0'
-if RUBY_VERSION <= '1.8.7'
-  gem 'i18n', '~> 0.6.11'
-end
 gem 'nokogiri', '~> 1.5.0'
 gem 'rspec-rails', '~> 2.14.1'
 gem 'test-unit'

gemfiles/Gemfile.rails-3.2

@@ -2,9 +2,6 @@ source 'https://rubygems.org'
 
 gem 'railties', '~> 3.2.0'
 gem 'activerecord', '~> 3.2.0'
-if RUBY_VERSION <= '1.8.7'
-  gem 'i18n', '~> 0.6.11'
-end
 gem 'nokogiri', '~> 1.5.0'
 gem 'rspec-rails', '~> 2.14.1'
 gem 'test-unit'