Bump 1.9.0

Author: tilfin

README.md

@@ -2,7 +2,7 @@ Ougai
 =====
 
 [![Gem Version](https://badge.fury.io/rb/ougai.svg)](https://badge.fury.io/rb/ougai)
-[![document](https://img.shields.io/badge/document-1.8.3-green.svg)](http://www.rubydoc.info/gems/ougai/)
+[![document](https://img.shields.io/badge/document-1.9.0-green.svg)](http://www.rubydoc.info/gems/ougai/)
 [![Build Status](https://travis-ci.org/tilfin/ougai.svg?branch=master)](https://travis-ci.org/tilfin/ougai)
 [![Code Climate](https://codeclimate.com/github/tilfin/ougai/badges/gpa.svg)](https://codeclimate.com/github/tilfin/ougai)
 [![Test Coverage](https://codeclimate.com/github/tilfin/ougai/badges/coverage.svg)](https://codeclimate.com/github/tilfin/ougai/coverage)

lib/ougai/version.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module Ougai
-  VERSION = '1.8.5'
+  VERSION = '1.9.0'
 end

ougai.gemspec

@@ -21,7 +21,7 @@ Gem::Specification.new do |spec|
   spec.test_files    = Dir['spec/**/*']
   spec.require_paths = ['lib']
 
-  spec.required_ruby_version = '>= 2.4.0'
+  spec.required_ruby_version = '>= 2.5.0'
 
   if RUBY_PLATFORM =~ /java/
     spec.platform = 'java'